The renal urate handling in humans has been
|
|
- Jonah Johnathan Poole
- 5 years ago
- Views:
Transcription
1 Renal Transport of Urate in Humans Françoise Roch-Ramel and Barbara Guisan The theory of the four-component model of urate excretion in humans is reevaluated, considering that a decrease in urate excretion induced by drugs like pyrazinamide or by endogenous compounds like lactate and ketone bodies might be a result of stimulation of urate reabsorption and not, as previously considered, of inhibition of urate secretion....transport mechanisms for urate... are localized in the proximal tubule... The renal urate handling in humans has been explained for many years by a four-component model. The purpose of this review is to reevaluate the validity of the theory behind this hypothetical model in the light of the transport mechanisms that were characterized recently in the apical membrane (brush-border membrane; BBM) of human proximal tubule. In humans, the uricase gene is not expressed, and uric acid is the end product of purine metabolism. It is a trioxypurine of which only the hydroxyl group in position 8 (pk a 5.75) is dissociable at physiological ph. The kidney plays a predominant role in its elimination, two-thirds of the daily production of uric acid being excreted by the renal route and the other one-third being eliminated by the gastrointestinal tract. In the plasma, 98% of the uric acid is dissociated and present as sodium urate, which is freely filtered, being bound by <5% to plasma proteins. Thus uric acid enters the proximal tubule in its anionic form, its concentration in the ultrafiltate being close to that of plasma. Both uric acid and urate, being hydrophilic, hardly permeate the tubular cells in the absence of facilitated mechanisms. The transport mechanisms for urate, as for organic anions in general, are localized in the proximal tubule (Fig. 1). In humans, urate is extensively reabsorbed, which results in excretion of ~10% of the filtered load of urate (FE urate = renal clearance of urate/glomerular filtration rate = 10%) (1). In the mammalian proximal tubule, micropuncture and microperfusion studies, as well as earlier stop-flow techniques, demonstrated that urate is bidirectionally transported with a predominance of reabsorption, in species such as rats, dogs, and Cebus monkeys, or secretion, as in pigs and rabbits (13). The distal parts of the nephron and the collecting ducts are hardly permeable to urate. A simplified scheme of urate handling by the nephron of reabsorbing mammals is provided in Fig. 1. In humans, experiments on renal handling of urate hitherto have been limited to the study of the effects of urate loading and of the different drugs interfering with urate excretion in vivo. Such experiments demonstrated a secretory transport for urate in a group of male gout patients with low filtration rates infused with uric acid and a uricosuric drug, when the FE urate rose from values below the filtration load (reabsorption) to values slightly exceeding the filtration load (secretion) (6). Urate secretion is also observed in hereditary hypouricemia, in which an increase in renal urate clearance is caused by a specific inborn error of urate transport (14). These observations suggest that urate is not only reabsorbed but also secreted in humans as in other mammals, reabsorption being predominant. Many attempts have been made to estimate the respective importance of the reabsorptive and secretory fluxes in pharmacological experiments, by measuring the effects of uricosuric and antiuricosuric drugs, in an endeavor to selectively inhibit the reabsorption or the secretion of urate. 80 F. Roch-Ramel is Professor and B. Guisan is a specialized technician from the Institut de Pharmacologie et Toxicologie, Bugnon 27, CH1005 Lausanne, Switzerland. Drug effect on urate excretion Many endogenous compounds and drugs / Int. Union Physiol. Sci./Am.Physiol. Soc.
2 FIGURE 1. Schematic representation of urate handling by the human nephron. Urate is secreted and reabsorbed along the proximal tubule (shown in gray). Reabsorption is predominant, and fractional excretion in the final urine approximates 10%. In some mammalian species secretion predominates (see text). interfere with the tubular transport of urate, which results either in uricosuria or in antiuricosuria; some of these are listed in Table 1. The effects of benzbromarone, probenecid, and tienilic acid and of the antiuricosuric drug pyrazinamide, in three groups of normal subjects, are shown in Table 2. Under the acute administration of therapeutic doses of the uricosuric drugs, the FE urate of normal subjects increased from control values between 7 and 10% to values between 30 and 54%, urate reabsorption being partially inhibited (Table 2). The acute administration of large oral doses of pyrazinamide (2 3 g) reduced the FE urate to values as low as % (Table 2). Pyrazinamide is a drug used in tuberculosis therapy. Its active metabolite, pyrazinoic acid (pyrazinoate), decreases the renal excretion of urate and thus is responsible for the hyperuricemia induced by pyrazinamide. The decrease in urate excretion by pyrazinamide, which was first interpreted as reflecting an increase in urate reabsorption, is most frequently considered to result from the inhibition of urate secretion. On the basis of the hypothesis that the oral administration of 2 3 g of pyrazinamide causes a selective and complete blockage of urate secretion, pyrazinamide has been used for measuring the importance of urate secretion in humans. The difference in the amount of urate excreted before and after pyrazinamide was thought to give a minimum estimate of urate secretion (9). Using such experimental approaches, secretion was estimated to represent about one-half the filtered amount of urate. For experimental purposes, and to tentatively uncover the defect in urate transport in gouty subjects, pyrazinamide and a uricosuric drug were occasionally given simultaneously, with the aim of inhibiting secretion and reabsorption, respectively. When pyrazinamide and benzbromarone or probenecid were administered together, the FE urate was below controls (Table 2), the uricosuric effect of benzbromarone and probenecid being depressed. The uricosuric effect of tienilic acid was reduced to a lesser extent by the administration of pyrazinamide. Considering that pyrazinamide is an inhibitor of urate secretion, and to interpret the blunting of the uricosuric effect by pyrazinamide, a four-component model of urate excretion in humans was postulated many years ago (2, 9). The four components of urate excretion This model includes 1) glomerular filtration, 2) a nearly complete reabsorption of filtered urate, and 3) secretion followed by 4) postsecretory reabsorption. This model postulates that most excreted urate derives from secretion, because after pyrazinamide administration in vivo ( inhibition of secretion ) only 1 2% of the filtered load is excreted (Table 2). Because of the low amount of urate left in tubular...most excreted urate derives from secretion... TABLE 1. Selection of substances that alter the renal tubular handling of urate Substances That Decrease Urate Secretion Lactate Acetoacetate -Hydroxybutyrate Nicotinate Pyrazinamide/pyrazinoate (tuberculostatic) *Drugs used clinically to treat hyperuricemia. Substances That Increase Urate Secretion Orotate Probenecid* Sulfinpyrazone* Benzbromarone* Losartan (antihypertensive drug) Tienilic acid (diuretic)* 81
3 TABLE 2. Fractional excretion of uric acid Control Uricosuric Pyrazinamide Pyrazinamide + (no drug) Drug 2 3 g po Uricosuric Drug References Benzbromarone (200 mg po) 7 ± ± ± ± Probenecid (500 mg iv) 8 ± ± ± ± Tienilic acid (500 mg po) 10 ± ± ± ± Fractional excretion (%) of uric acid by 3 groups of healthy subjects with normal plasma concentration of urate (~300µM)....a urate/anion exchanger has been identified fluid during the inhibition of urate secretion, reabsorption is negligible, and inhibition of reabsorption by uricosuric drugs can only induce a minor increase in urate excretion. Consequently, a postsecretory site of urate reabsorption was postulated, which would be the site of action of uricosuric drugs. This ingenious model, which fits with the observed effects of drugs, is valid only if pyrazinamide inhibits urate secretion, which was never demonstrated. Indeed, there are a few observations that suggest that pyrazinamide is not an inhibitor of urate secretion. First, animals that eliminate urate by net secretion, chicken, rabbits and pigs, do not respond to pyrazinoate, the active metabolite of pyrazinamide (1). Second, experiments by Guggino and Aronson (4) on urate transport in BBM vesicles of dogs strongly suggest that pyrazinoate could stimulate urate reabsorption. Similar experiments in human BBM vesicles, reported below, also support pyrazinamide stimulation of reabsorption. Transport mechanisms in membranes of the human proximal tubule In urate-reabsorbing nonprimate mammals, e.g., rats and dogs, a urate/anion exchanger has been identified in the BBM of the proximal tubule, which accepts multiple monovalent organic anions, aliphatic or aromatic, including p-aminohippurate, as well as chloride and hydroxyl ions (5). The physiological role of the anion exchanger was demonstrated in situ in tubular and peritubular capillary perfusion experiments. Such a urate/anion exchanger is absent in rabbits and pigs, which predominantly secrete urate. These species differences strongly suggest that the urate/anion exchanger is an essential mechanism for urate reabsorption. The presence of a similar urate/anion exchanger was demonstrated in human BBM vesicles prepared from normal sections of human kidneys excised because of carcinoma (Fig. 2, left, mechanism 1) (10). The substrate affinities for the human anion exchanger are largely identical to those of dogs, with the exception that p-aminohippurate and hydroxyl ions are not substrates. The aromatic substrates pyrazinoate, nicotinate, and orotate have about the same affinity as urate for the anion exchanger. The affinity of the aliphatic compounds lactate, β- hydroxybutyrate, and acetoacetate is about one order of magnitude lower. These substrates, when loaded in the BBM vesicles, stimulate urate uptake (trans stimulation), but when added to the uptake medium, they inhibit urate uptake (cis inhibition) (10). Substrates such as lactate, nicotinate, and pyrazinoate, beside being substrates for the exchanger, are also transported by sodium cotransport and can stimulate urate uptake by BBM vesicles, when added to the uptake medium, in the presence of an inward directed sodium gradient (cis stimulation) (10, 12). The uricosuric drugs probenecid, benzbromarone, sulfinpyrazone, tienilic acid, salicylate, and losartan cis inhibit urate uptake when added to the uptake medium (11). In addition to the urate/anion exchanger, a voltage-sensitive pathway for urate transport has been identified in human BBM (Fig. 2, left, mechanism 2). The affinity of this pathway for the substrates of the anion exchanger, and in particular for pyrazinoate and the uricosuric drugs, is about one order of magnitude lower than the affinities of the anion exchanger (10). Because of the cell electronegativity, the voltage-sensitive pathway should favor cell-to-lumen efflux in vivo. The urate transport mechanisms in the basolateral membrane are still undefined. A voltage-sensitive transport (Fig. 2, left, mechanism 3) might be the mechanism facilitating urate efflux to the interstitium (second membrane step in reabsorption). The mechanisms involved in urate transport from peritubular space to the proximal cell, the first membrane step in secretion, have not been elucidated, although we looked for a urate/anion exchanger. In the pig, a secreting mammal, urate is transported across the basolateral membrane by a mechanism similar to that of p-aminohippurate, a urate/α-ketoglutarate exchanger; however, in humans urate is transported by mechanisms other than that of p- aminohippurate (10). Physiological role of the apical urate/anion exchanger We postulate that from the lumen, urate enters the proximal tubular cell in exchange for intra-
4 ketone bodies results from a stimulation of urate reabsorption and not, as postulated earlier, by an inhibition of urate secretion. FIGURE 2. Scheme of membrane mechanisms involved in urate reabsorption. Top: urate transport mechanisms of human proximal tubules are shown on left. Mechanism 1, urate/anion exchanger; mechanism 2, apical voltage-sensitive pathway; mechanism 3, basolateral voltage-sensitive pathway. Physiological substrates for the exchanger (X - ) are lactate, β-hydroxybutyrate, acetoacetate, etc. Many of these substrates are compounds reabsorbed from the proximal tubule by sodium cotransport. On right, cooperation of a sodiumanion cotransport (4) with the urate/anion exchanger (1) is shown. From the lumen, urate enters the cells in exchange for X -, which enters the lumen. Urate leaves the cell through the basolateral voltage-sensitive pathway (3), and X - is recycled to the cell by sodium cotransport; from the cell it is again available for urate exchange. Bottom: administration of nicotinate and pyrazinoate (PZA - ) provides additional substrates for the urate/anion exchanger. Both anions are taken into the cell by sodium cotransport, from where they stimulate urate uptake. From the lumen they are recycled again to the cell by sodium cotransport (4). In contrast, orotate, which is not transported with sodium, competes with urate for transport through the urate/anion exchanger (1) and thus decreases the reabsorption of urate. Uricosuric drugs such as benzbromarone and probenecid act in a similar way at the luminal surface of the tubular cells, reducing access of the urate to the urate/anion exchanger. Modified from Ref. 10 with permission. cellular anions (X - ; Fig. 2, right, mechanism 1). This is the first step of urate reabsorption. From the tubular lumen anions such as lactate, β- hydroxybutyrate, and acetoacetate are recycled by sodium cotransport (mechanism 4), thereby providing a constant gradient of intracellular anions, which drives urate into the cells. However, these anions are also produced by intracellular metabolism. When the amount of intracellular anions available for exchange with urate is increased, reabsorption might be stimulated, which results in a decrease in urate excretion and in hyperuricemia. This is what happens in humans during fasting or starvation because of the accumulation of ketone bodies or also during experimental infusion of β-hydroxybutyrate or acetoacetate to normal subjects (3). We suggest that the hyperuricemia induced by lactate and Mechanism of action of uricosuric and antiuricosuric agents The urate/anion exchanger might be the site of action of uricosuric as well as antiuricosuric agents, depending on their presence either in the lumen or in the proximal tubular cells. This is illustrated by the comparison of the in vivo effect of orotate and nicotinate, two substrates that have a similar affinity for the urate/anion exchanger (12). In humans orotate is uricosuric, whereas nicotinate is antiuricosuric (3). The main difference between the two substrates is that nicotinate is reabsorbed from the proximal tubule by sodium cotransport, whereas orotate is not. Both nicotinate and orotate can stimulate urate transport through the urate/anion exchanger (Fig. 2, bottom), but only nicotinate is recycled into the cell by sodium cotransport. In contrast to nicotinate, orotate remains in the lumen, where it competes with urate cellular uptake, which explains its uricosuric effect. It has long been recognized that uricosuric drugs act from the tubular lumen. All uricosuric compounds investigated in the human BBM vesicle model inhibited urate uptake through the urate/anion exchanger. In vivo, they compete with urate in the lumen for the exchanger, either for binding or for transport, the net result being uricosuria. Pyrazinoate, the active metabolite of pyrazinamide, is a pyrazine analog of nicotinate. Like nicotinate it is reabsorbed by a sodium cotransport mechanism, and most probably it stimulates urate uptake by the proximal cells in a way similar to nicotinate. When pyrazinamide is administered and metabolized to pyrazinoate, the cooperation of the urate/pyrazinoate exchange and of the sodium-pyrazinoate cotransport (Fig. 2, bottom) provides a constant increase in the anion gradient that stimulates urate reabsorption. Why is the uricosuric effect of drugs blunted by pyrazinamide? Two points need to be considered. First, the reabsorptive capacity of the human kidney is large. When the filtered load of urate of normal subjects is doubled, following several days ingestion of yeast RNA and pyrazinamide administration, the reabsorption of urate is also doubled, the reabsorptive transport still not being saturated (9). Second, when therapeutic doses of uricosuric drugs are administered to normal subjects, the reabsorption of urate is only partially inhibited...nicotinate is reabsorbed from the proximal tubule... 83
5 ...secretion... contributes only in a minor way to urate excretion... (Table 2); an amount at least equal to 40 50% of the filtrated load is still reabsorbed. We postulate that the reabsorptive capacity of the human proximal tubule is such that even if part of the reabsorptive mechanism is inhibited by uricosuric drugs, the cellular recycling of pyrazinoate is efficient enough to stimulate the reabsorption of urate through the urate/anion exchanger. Urate secretion Urate secretion was suggested to be important because of the strong decrease of urate excretion by pyrazinamide. It is now evident from the human BBM vesicle studies that pyrazinamide has a major effect on reabsorption and that urate secretion in humans has been largely overestimated. At present the role of secretion is undefined; we suggest that it contributes only in a minor way to urate excretion in normal individuals. Conclusions The urate handling by the human kidney does not seem to proceed according to the four-component model proposed earlier. Secretion appears to be minor, and reabsorption and secretion might coexist along the whole proximal tubule. In humans urate reabsorption in the kidney is mediated mainly by the urate/anion exchanger of the apical membrane of the proximal tubule. Intracellular substrates for the exchanger stimulate the reabsorption of urate, whereas uricosuric agents inhibit urate reabsorption from the lumen. Urate leaves the cell through the basolateral voltage-sensitive pathway, along its electrochemical gradient. The authors thank Dr. H. A. Simmonds and Prof. J. Diezi for their critical reading of the manuscript. The authors work was supported by grants from the Swiss National Fund for Scientific Research. References 1. Cameron, J. S., F. Moro, and H. A. Simmonds. Uric acid and the kidney. In: Oxford Textbook of Clinical Nephrology (2nd ed.), edited by A. M. Davison, J. S. Cameron, J. P. Grünfeld, D. N. S. Kerr, E. Ritz, and C. G. Winearls. London: Oxford Medical, 1997, vol. 2, p Diamond, H. S., and J. S. Paolino. Evidence for a postsecretory reabsorptive site for uric acid in man. J. Clin. Invest. 52: , Emmerson, B. T. Abnormal urate excretion associated with renal and systemic disorders, drugs and toxins. In: Uric Acid, edited by W. N. Kelley and I. M. Weiner. Berlin: Springer, 1978, p Guggino, S. E., and P. S. Aronson. Paradoxical effects of pyrazinoate and nicotinate on urate transport in dog renal microvillus membranes. J. Clin. Invest. 76: , Guggino, S. E., G. J. Martin, and P. S. Aronson. Specificity and modes of the anion exchanger in dog renal microvillus membranes. Am. J. Physiol. 244 (Renal Fluid Electrolyte Physiol. 13): F612 F621, Gutman, A. B., T. S. Fan Yü, and L. Berger. Tubular secretion of urate in man. J. Clin. Invest. 38: , Moriwaki, Y., T. Yamamoto, S. Takahashi, T. Hada, and K. Higashino. Analysis of uric acid transport in renal tubules using benzbromarone and pyrazinamide. Int. J. Clin. Pharmacol. Ther. Toxicol. 28: 84 88, Prasad, D. R., I. M. Weiner, and T. H. Steele. Diureticinduced uricosuria: interaction with pyrazinoate transport in man. J. Pharmacol. Exp. Ther. 200: 58 64, Rieselbach, R. E., and T. H. Steele. Influence of the kidney upon urate homeostasis in health and disease. Am. J. Med. 56: , Roch-Ramel, F., and J. Diezi. Renal transport of organic ions and uric acid. In: Diseases of the Kidney (6th ed.), edited by R. W. Schrier and C. W. Gottschalk. Boston: Little, Brown, 1997, p Roch-Ramel, F., B. Guisan, and J. Diezi. Effect of uricosuric and antiuricosuric agents on urate transport in human brush-border membrane vesicles. J. Pharmacol. Exp. Ther. 280: , Roch-Ramel, F., B. Guisan, P. Jaeger, and J. Diezi. Transport of urate and other anions by anion exchange in human brush-border membrane vesicles. Cell. Physiol. Biochem. 6: 60 71, Roch-Ramel, F., and G. Peters. Urinary excretion of uric acid in nonhuman mammalian species. In: Uric Acid, edited by W. N. Kelley and I. M. Weiner. Berlin: Springer, 1978, p Sperling, O. Hereditary renal hypouricemia. In: The Metabolic and Molecular Basis of Inherited Disease (7th ed.), edited by C. R. Scriver, A. L. Beaudet, W. S. Sly, and D. Valle. New York: McGraw-Hill, 1995, p Steele, T. H. and G. Boner. Origins of the uricosuric response. J. Clin. Invest. 52: , Science may be described as the art of systematic over-simplification. Karl Popper, to a reporter from the London Observer,
Evidence for a Postsecretory Reabsorptive
Evidence for a Postsecretory Reabsorptive Site for Uric Acid in Man HERBERT S. DIAumoi and JAMEs S. PAOLINO From the Department of Medicine, State University of New York Downstate Medical Center, Brooklyn,
More informationIndirect coupling between sodium and urate transport in the
Kidney International, Vol. 36 (1989), pp. 378 384 Indirect coupling between sodium and urate transport in the proximal tubule ANDREW M. KAHN University of Texas Medical School, Department of Medicine,
More informationRENAL SYSTEM 2 TRANSPORT PROPERTIES OF NEPHRON SEGMENTS Emma Jakoi, Ph.D.
RENAL SYSTEM 2 TRANSPORT PROPERTIES OF NEPHRON SEGMENTS Emma Jakoi, Ph.D. Learning Objectives 1. Identify the region of the renal tubule in which reabsorption and secretion occur. 2. Describe the cellular
More information11/05/1431. Urine Formation by the Kidneys Tubular Processing of the Glomerular Filtrate
Urine Formation by the Kidneys Tubular Processing of the Glomerular Filtrate Chapter 27 pages 327 347 1 OBJECTIVES At the end of this lecture you should be able to describe: Absorptive Characteristics
More informationRenal Excretion of Drugs
Renal Excretion of Drugs 3 1 Objectives : 1 Identify main and minor routes of Excretion including renal elimination and biliary excretion 2 Describe its consequences on duration of drugs. For better understanding:
More informationCollin College. BIOL Anatomy & Physiology. Urinary System. Summary of Glomerular Filtrate
Collin College BIOL. 2402 Anatomy & Physiology Urinary System 1 Summary of Glomerular Filtrate Glomerular filtration produces fluid similar to plasma without proteins GFR ~ 125 ml per min If nothing else
More informationExcretion of Drugs. Prof. Hanan Hagar Pharmacology Unit Medical College
Excretion of Drugs Prof. Hanan Hagar Pharmacology Unit Medical College Excretion of Drugs By the end of this lecture, students should be able to! Identify main and minor routes of excretion including renal
More informationPhysio 12 -Summer 02 - Renal Physiology - Page 1
Physiology 12 Kidney and Fluid regulation Guyton Ch 20, 21,22,23 Roles of the Kidney Regulation of body fluid osmolarity and electrolytes Regulation of acid-base balance (ph) Excretion of natural wastes
More informationDiuretics having the quality of exciting excessive excretion of urine. OED. Inhibitors of Sodium Reabsorption Saluretics not Aquaretics
Diuretics having the quality of exciting excessive excretion of urine. OED Inhibitors of Sodium Reabsorption Saluretics not Aquaretics 1 Sodium Absorption Na Entry into the Cell down an electrochemical
More informationNon-protein nitrogenous substances (NPN)
Non-protein nitrogenous substances (NPN) A simple, inexpensive screening test a routine urinalysis is often the first test conducted if kidney problems are suspected. A small, randomly collected urine
More informationNa + Transport 1 and 2 Linda Costanzo, Ph.D.
Na + Transport 1 and 2 Linda Costanzo, Ph.D. OBJECTIVES: After studying this lecture, the student should understand: 1. The terminology applied to single nephron function, including the meaning of TF/P
More information014 Chapter 14 Created: 9:25:14 PM CST
014 Chapter 14 Created: 9:25:14 PM CST Student: 1. Functions of the kidneys include A. the regulation of body salt and water balance. B. hydrogen ion homeostasis. C. the regulation of blood glucose concentration.
More informationRenal System Physiology
M58_MARI0000_00_SE_EX09.qxd 7/18/11 2:37 PM Page 399 E X E R C I S E 9 Renal System Physiology Advance Preparation/Comments 1. Prior to the lab, suggest to the students that they become familiar with the
More informationRenal handling of uric acid in normal and gouty
Annals of the Rheumatic Diseases, 1980, 39, 173179 Renal handling of uric acid in normal and gouty subjects: evidence for a 4component system DENNIS J. LEVINSON AND LEIF B. SORENSEN From the Department
More informationNORMAL POTASSIUM DISTRIBUTION AND BALANCE
NORMAL POTASSIUM DISTRIBUTION AND BALANCE 98% of body potassium is contained within cells, principally muscle cells, and is readily exchangeable. Only 2% is in ECF. Daily intake exceeds the amount in ECF.
More informationRENAL PHYSIOLOGY, HOMEOSTASIS OF FLUID COMPARTMENTS
RENAL PHYSIOLOGY, HOMEOSTASIS OF FLUID COMPARTMENTS (2) Dr. Attila Nagy 2017 TUBULAR FUNCTIONS (Learning objectives 54-57) 1 Tubular Transport About 99% of filtrated water and more than 90% of the filtrated
More informationAnswers and Explanations
Answers and Explanations 1. The answer is D [V B 4 b]. Distal K + secretion is decreased by factors that decrease the driving force for passive diffusion of K + across the luminal membrane. Because spironolactone
More information1. remove: waste products: urea, creatinine, and uric acid foreign chemicals: drugs, water soluble vitamins, and food additives, etc.
Making Water! OR is it really Just Water Just Ask the Nephron!! Author: Patricia L. Ostlund ostlundp@faytechcc.edu (910) 678-9892 Fayetteville Technical Community College Fayetteville, NC 28303 Its just
More informationRenal Physiology II Tubular functions
Renal Physiology II Tubular functions LO. 42, 43 Dr. Kékesi Gabriella Basic points of renal physiology 1. Glomerular filtration (GF) a) Ultrafiltration 2. Tubular functions active and passive a) Reabsorption
More informationUnit 2b: EXCRETION OF DRUGS. Ms.M.Gayathri Mpharm (PhD) Department of Pharmaceutics Krishna Teja Pharmacy college Subject code: 15R00603 (BPPK)
Unit 2b: EXCRETION OF DRUGS By Ms.M.Gayathri Mpharm (PhD) Department of Pharmaceutics Krishna Teja Pharmacy college Subject code: 15R00603 (BPPK) Excretion, along with metabolism and tissue redistribution,
More informationNephron Function and Urine Formation. Ms. Kula December 1, 2014 Biology 30S
Nephron Function and Urine Formation Ms. Kula December 1, 2014 Biology 30S The Role of the Nephron In order for the body to properly function and maintain homeostasis, the amount of dissolved substances
More informationClinical Biochemistry department/ College of medicine / AL-Mustansiriyah University
Clinical Biochemistry department/ College of medicine / AL-Mustansiriyah University Dr. Ali al-bayati NUCLEOTIDE METABOLISM Lec. 3 The salvage pathway of purine synthesis Purines that result from the normal
More informationRenal Physiology - Lectures
Renal Physiology - Lectures Physiology of Body Fluids PROBLEM SET, RESEARCH ARTICLE Structure & Function of the Kidneys Renal Clearance & Glomerular Filtration PROBLEM SET Regulation of Renal Blood Flow
More informationRenal System Dr. Naim Kittana Department of Biomedical Sciences Faculty of Medicine & Health Sciences An-Najah National University
Renal System Dr. Naim Kittana Department of Biomedical Sciences Faculty of Medicine & Health Sciences An-Najah National University Declaration The content and the figures of this seminar were directly
More informationPhysiology Lecture 2. What controls GFR?
Physiology Lecture 2 Too much blood is received by the glomerular capillaries, this blood contains plasma, once this plasma enters the glomerular capillaries it will be filtered to bowman s space. The
More informationPARTS OF THE URINARY SYSTEM
EXCRETORY SYSTEM Excretory System How does the excretory system maintain homeostasis? It regulates heat, water, salt, acid-base concentrations and metabolite concentrations 1 ORGANS OF EXCRETION Skin and
More informationDiuretic Agents Part-2. Assistant Prof. Dr. Najlaa Saadi PhD Pharmacology Faculty of Pharmacy University of Philadelphia
Diuretic Agents Part-2 Assistant Prof. Dr. Najlaa Saadi PhD Pharmacology Faculty of Pharmacy University of Philadelphia Potassium-sparing diuretics The Ion transport pathways across the luminal and basolateral
More informationRENAL FUNCTION An Overview
RENAL FUNCTION An Overview UNIVERSITY OF PNG SCHOOL OF MEDICINE AND HEALTH SCIENCES DIVISION OF BASIC MEDICAL SCIENCES DISCIPLINE OF BIOCHEMISTRY & MOLECULAR BIOLOGY PBL MBBS II SEMINAR VJ. Temple 1 Kidneys
More informationGlucosuria: Diabetes Mellitus
172 PHYSIOLOGY CASES AND PROBLEMS Case 30 Glucosuria: Diabetes Mellitus David Mandel was diagnosed with type I (insulin-dependent) diabetes mellitus when he was 12 years old, right after he started middle
More informationOsmotic Regulation and the Urinary System. Chapter 50
Osmotic Regulation and the Urinary System Chapter 50 Challenge Questions Indicate the areas of the nephron that the following hormones target, and describe when and how the hormones elicit their actions.
More informationCollin County Community College RENAL PHYSIOLOGY
Collin County Community College BIOL. 2402 Anatomy & Physiology WEEK 12 Urinary System 1 RENAL PHYSIOLOGY Glomerular Filtration Filtration process that occurs in Bowman s Capsule Blood is filtered and
More informationIntroduction. Acids, Bases and ph; a review
0 P a g e Introduction In this sheet, we discuss acidbase balance in our body and the role of kidneys in its establishment. Arrangement of topics is different from that of the lecture, to assure consistency
More informationVertebrates possess kidneys: internal organs which are vital to ion and water balance and excretion.
The Kidney Vertebrates possess kidneys: internal organs which are vital to ion and water balance and excretion. The kidney has 6 roles in the maintenance of homeostasis. 6 Main Functions 1. Ion Balance
More informationRenal physiology II. Basic renal processes. Dr Alida Koorts BMS
Renal physiology II Basic renal processes Dr Alida Koorts BMS 7-12 012 319 2921 akoorts@medic.up.ac.za Basic renal processes 1. filtration 2. reabsorption 3. secretion Glomerular filtration The filtration
More informationRenal Physiology. April, J. Mohan, PhD. Lecturer, Physiology Unit, Faculty of Medical Sciences, U.W.I., St Augustine.
Renal Physiology April, 2011 J. Mohan, PhD. Lecturer, Physiology Unit, Faculty of Medical Sciences, U.W.I., St Augustine. Office : Room 105, Physiology Unit. References: Koeppen B.E. & Stanton B.A. (2010).
More informationSodium and chlorine transport
Kidney physiology 2 Sodium and chlorine transport The kidneys help to maintain the body's extracellular fluid (ECF) volume by regulating the amount of Na+ in the urine. Sodium salts (predominantly NaCl)
More informationAfter studying this lecture, you should be able to...
Reabsorption of Salt and Water After studying this lecture, you should be able to... 1. Define the obligatory water loss. 2. Describe the mechanism of Na ++ reabsorption in the distal tubule and explain
More informationCONTROLLING THE INTERNAL ENVIRONMENT
AP BIOLOGY ANIMAL FORM & FUNCTION ACTIVITY #5 NAME DATE HOUR CONTROLLING THE INTERNAL ENVIRONMENT KIDNEY AND NEPHRON NEPHRON FUNCTIONS Animal Form & Function Activity #5 page 1 NEPHRON STRUCTURE NEPHRON
More informationAcid-Base Balance 11/18/2011. Regulation of Potassium Balance. Regulation of Potassium Balance. Regulatory Site: Cortical Collecting Ducts.
Influence of Other Hormones on Sodium Balance Acid-Base Balance Estrogens: Enhance NaCl reabsorption by renal tubules May cause water retention during menstrual cycles Are responsible for edema during
More informationHUMAN SUBJECT 1. Syracuse, N. Y.) the urine of increasing quantities of these buffers, it has been found in man as in the dog that (1)
THE RENAL REGULATION OF ACID-BASE BALANCE IN MAN. II. FACTORS AFFECTING THE EXCRETION OF TITRATABLE ACID BY THE NORMAL HUMAN SUBJECT 1 By W. A. SCHIESS, J. L. AYER, W. D. LOTSPEICH AND R. F. PITTS WITH
More informationPhysiology of Excretory Systems
Physiology of Excretory Systems Fig 12-2 (a) Urea is formed by the ornithine-urea cycle in most vertebrates. Because ATP is required for the first step, nitrogen excretion in ureotelic animals is more
More informationRenal Reabsorption & Secretion
Renal Reabsorption & Secretion Topics for today: Nephron processing of filtrate Control of glomerular filtration Reabsorption and secretion Examples of solute clearance rates Hormones affecting kidney
More informationDIURETICS-2. Dr. Shariq Syed. Shariq AIKC/TYB/2014
DIURETICS-2 Dr. Syed Structure of Kidney Blood filtered by functional unit: Nephron Except for cells, proteins, other large molecules, rest gets filtered Structure of Kidney 3 major regions of nephron
More information150 mm HCO How Does the Pancreas Do It? Clues from Computer Modelling of the Duct Cell
JOP. J. Pancreas (Online) 2001; 2(4 Suppl):198202. 150 mm How Does the Pancreas Do It? Clues from Computer Modelling of the Duct Cell Yoshiro Sohma 1, Michael A Gray 2, Yusuke Imai 1, Barry E Argent 2
More informationRENAL TUBULAR ACIDOSIS An Overview
RENAL TUBULAR ACIDOSIS An Overview UNIVERSITY OF PNG SCHOOL OF MEDICINE AND HEALTH SCIENCES DISCIPLINE OF BIOCHEMISTRY & MOLECULAR BIOLOGY CLINICAL BIOCHEMISTRY PBL MBBS IV VJ. Temple 1 What is Renal Tubular
More informationUrinary System. consists of the kidneys, ureters, urinary bladder and urethra
Urinary System 1 Urinary System consists of the kidneys, ureters, urinary bladder and urethra 2 Location of Kidneys The kidneys which are positioned retroperitoneally lie on either side of the vertebral
More informationFunctions of Proximal Convoluted Tubules
1. Proximal tubule Solute reabsorption in the proximal tubule is isosmotic (water follows solute osmotically and tubular fluid osmolality remains similar to that of plasma) 60-70% of water and solute reabsorption
More informationHuman Physiology - Problem Drill 17: The Kidneys and Nephronal Physiology
Human Physiology - Problem Drill 17: The Kidneys and Nephronal Physiology Question No. 1 of 10 Instructions: (1) Read the problem statement and answer choices carefully, (2) Work the problems on paper
More informationEFFECTS OF PROBENECID, SODIUM SALICYLATE, 2,4-DINITROPHENOL AND PYRAZINAMIDE ON RENAL SECRETION OF URIC ACID IN CHICKENS
8189 EFFECTS OF PROBENECID, SODIUM SALICYLATE, 2,4-DINITROPHENOL AND PYRAZINAMIDE ON RENAL SECRETION OF URIC ACID IN CHICKENS BOHDAN R. NECHAY AND LARYSSA NECHAY Department of Pharmacology and Therapeutics,
More informationExcretory System 1. a)label the parts indicated above and give one function for structures Y and Z
Excretory System 1 1. Excretory System a)label the parts indicated above and give one function for structures Y and Z W- X- Y- Z- b) Which of the following is not a function of the organ shown? A. to produce
More informationBIOL 2402 Renal Function
BIOL 2402 Renal Function Dr. Chris Doumen Collin County Community College 1 Renal Clearance and GFR Refers to the volume of blood plasma from which a component is completely removed in one minute by all
More informationCopyright 2009 Pearson Education, Inc. Copyright 2009 Pearson Education, Inc. Figure 19-1c. Efferent arteriole. Juxtaglomerular apparatus
/6/0 About this Chapter Functions of the Kidneys Anatomy of the urinary system Overview of kidney function Secretion Micturition Regulation of extracellular fluid volume and blood pressure Regulation of
More informationPhysiology (4) 2/4/2018. Wael abu-anzeh
Physiology (4) 2/4/2018 Wael abu-anzeh In the previous lectures we have discussed the filtration and the reabsorption processes but in this lecture we will talk about the factor that will regulate or control
More informationThe principal functions of the kidneys
Renal physiology The principal functions of the kidneys Formation and excretion of urine Excretion of waste products, drugs, and toxins Regulation of body water and mineral content of the body Maintenance
More informationEffect of Urine Flow Rate on Uric Acid Excretion in Man
Effect of Urine Flow Rate on Uric Acid Excretion in Man Herbert S. Diamond, Robert Lazarus, David Kaplan and David Halberstam The effect of alteration in rate of urine flow on renal excretion of uric acid
More informationUrinary System. Dr. ZHANG Xiong. Dept. of Physiology. ZJU School of Medicine. QUESTION 6
Urinary System Dr. ZHANG Xiong Dept. of Physiology ZJU School of Medicine http://10.71.121.158 Copyright@ Xiong Zhang QUESTION 6 How is the filtrate reabsorbed in tubular system? Copyright@ Xiong Zhang
More informationFunctional morphology of kidneys Clearance
Functional morphology of kidneys Clearance Assoc. Prof. MUDr. Markéta Bébarová, Ph.D. Department of Physiology Faculty of Medicine, Masaryk University This presentation includes only the most important
More informationCh 17 Physiology of the Kidneys
Ch 17 Physiology of the Kidneys Review Anatomy on your own SLOs List and describe the 4 major functions of the kidneys. List and explain the 4 processes of the urinary system. Diagram the filtration barriers
More informationBCH 450 Biochemistry of Specialized Tissues
BCH 450 Biochemistry of Specialized Tissues VII. Renal Structure, Function & Regulation Kidney Function 1. Regulate Extracellular fluid (ECF) (plasma and interstitial fluid) through formation of urine.
More informationosmoregulation mechanisms in gills, salt glands, and kidneys
Ionic & Osmotic Homeostasis osmoregulation mechanisms in gills, salt glands, and kidneys extracellular intracellular 22 23 Salt Secretion: recycle Figure in Box 26.2 Hill et al. 2004 active Down electrochemical
More informationCh 19: The Kidneys. Functional unit of kidneys:?? Developed by John Gallagher, MS, DVM
Ch 19: The Kidneys Homeostatic regulation of ECF volume and BP Osmolarity 290 mosm Ion balance Na+ and K+, etc. ph (acid-base balance Excretion of wastes & foreign substances Hormone production EPO Renin
More informationAnatomy/Physiology Study Guide: Unit 9 Excretory System
Anatomy/Physiology Study Guide: Unit 9 Excretory System 1) In the space below, list the primary structures (organs) and their corresponding functions. Structures: Functions: KIDNEY 1) URETER BLADDER URETHRA
More informationEarly Filtrate Processing Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.
Early Filtrate Processing Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com) Page 1. Introduction Once the filtrate is formed, the early
More informationApril 08, biology 2201 ch 11.3 excretion.notebook. Biology The Excretory System. Apr 13 9:14 PM EXCRETORY SYSTEM.
Biology 2201 11.3 The Excretory System EXCRETORY SYSTEM 1 Excretory System How does the excretory system maintain homeostasis? It regulates heat, water, salt, acid base concentrations and metabolite concentrations
More informationRenal Clearance. Dr. Eman El Eter
Renal Clearance Dr. Eman El Eter Concept of clearance Clearance is the volume of plasma that is completely cleared of a substance each minute. Example: Renal clearance of Substance X is defined as the
More informationRenal-Related Questions
Renal-Related Questions 1) List the major segments of the nephron and for each segment describe in a single sentence what happens to sodium there. (10 points). 2) a) Describe the handling by the nephron
More informationDrugs Used in Gout. Knox Van Dyke. GENERIC NAME Allopurinol 445 Colchicine 443 Indomethacin 446 Oxyphenbutazone 446
37 Drugs Used in Gout Knox Van Dyke DRUG LIST GENERIC NAME PAGE GENERIC NAME PAGE Allopurinol 445 Colchicine 443 Indomethacin 446 Oxyphenbutazone 446 Oxypurinol 446 Phenylbutazone 446 Probenecid 445 Sulfinpyrazone
More informationRenal Quiz - June 22, 21001
Renal Quiz - June 22, 21001 1. The molecular weight of calcium is 40 and chloride is 36. How many milligrams of CaCl 2 is required to give 2 meq of calcium? a) 40 b) 72 c) 112 d) 224 2. The extracellular
More informationExcretory Lecture Test Questions Set 1
Excretory Lecture Test Questions Set 1 1. The separation and ejection of metabolic wastes, usually in aqueous solution, is: a. reabsorption b. secretion c. filtration d. excretion e. endocrinology 2. Besides
More informationWater Reabsorption and the Effect of Diuretics on Urine Formation Patricia J. Clark, Ph.D. Department of Biology, IUPUI
Water Reabsorption and the Effect of Diuretics on Urine Formation Patricia J. Clark, Ph.D. Department of Biology, IUPUI This activity may be done in conjunction with a more traditional urinalysis lab.
More informationRenal Pharmacology. Diuretics: Carbonic Anhydrase Inhibitors Thiazides Loop Diuretics Potassium-sparing Diuretics BIMM118
Diuretics: Carbonic Anhydrase Inhibitors Thiazides Loop Diuretics Potassium-sparing Diuretics Renal Pharmacology Kidneys: Represent 0.5% of total body weight, but receive ~25% of the total arterial blood
More informationThe Renal Excretion of Oxypurines *
Journal of Clinical Investigation Vol. 44, No. 4, 1965 The Renal Excretion of Oxypurines * STEPHEN GOLDFINGER,t JAMES R. KLINENBERG,4 AND J. EDWIN SEEGMILLER (From the National Institute of Arthritis and
More informationYou should know the T max for any substance that you use and for PAH ; T max = mg / min
Tubular function - What is clearance? o clearance referred to the theoretical volume of plasma from which a substance is cleared ( cleaned ) over a period of time and so its unit would be ((ml/min)) -
More informationURICOSURIC AGENTS GEORGE M FANELLI, JR.
853 URICOSURIC AGENTS GEORGE M FANELLI, JR. By definition a uricosuric agent is one that facilitates the renal excretion of uric acid presumably by specific inhibition of its tubular reabsorption and secretion.
More informationPrinciples of Renal Physiology. 4th Edition
Principles of Renal Physiology 4th Edition Principles of Renal Physiology 4th Edition Chris Lote Professor of Experimental Nephrology, University of Birmingham, UK SPRINGER SCIENCE+BUSINESS MEDIA, B.V.
More informationRenal excretion of urate: Factors determining the actions of drugs
Kidney International, Vol. 18 (1980), pp. 665-676 Renal excretion of urate: Factors determining the actions of drugs F1NçoIsE ROCH-RAMEL and IRWIN M. WEINER Institut de Pharmacologic de l'université de
More informationQUIZ/TEST REVIEW NOTES SECTION 2 RENAL PHYSIOLOGY FILTRATION [THE KIDNEYS/URINARY SYSTEM] CHAPTER 19
1 QUIZ/TEST REVIEW NOTES SECTION 2 RENAL PHYSIOLOGY FILTRATION [THE KIDNEYS/URINARY SYSTEM] CHAPTER 19 Learning Objectives: Differentiate the following processes: filtration, reabsorption, secretion, excretion
More informationNephron Anatomy Nephron Anatomy
Kidney Functions: (Eckert 14-17) Mammalian Kidney -Paired -1% body mass -20% blood flow (Eckert 14-17) -Osmoregulation -Blood volume regulation -Maintain proper ion concentrations -Dispose of metabolic
More informationCASE 27. What is the response of the kidney to metabolic acidosis? What is the response of the kidney to a respiratory alkalosis?
CASE 27 A 21-year-old man with insulin-dependent diabetes presents to the emergency center with mental status changes, nausea, vomiting, abdominal pain, and rapid respirations. On examination, the patient
More informationD fini n tion: p = = -log [H+] ph=7 me m an s 10-7 Mol M H+ + (100 nmol m /l); ) p ; H=8 me m an s 10-8 Mol M H+ + (10 (10 n nmol m /l) Nor
Definition: ph regulation ph = -log [H + ] ph=7 means 10-7 Mol H + (100 nmol/l); ph=8 means 10 Normal plasma value: 7.35-7.45; 7.45; (H Acidosis: ph7.45 Intracellular ph = 7.1-7.3
More informationRENAL PHYSIOLOGY WESTMEAD PRIMARY EXAM
RENAL PHYSIOLOGY WESTMEAD PRIMARY EXAM RENAL PHYSIOLOGY - ANATOMY Glomerulus + renal tubule Each kidney has 1.3 million nephrons Cortical nephrons (85%) have shorter Loop of Henle than Juxtamedullary nephrons
More informationNephron Structure inside Kidney:
In-Depth on Kidney Nephron Structure inside Kidney: - Each nephron has two capillary regions in close proximity to the nephron tubule, the first capillary bed for fluid exchange is called the glomerulus,
More informationGlomerular Capillary Blood Pressure
Glomerular Capillary Blood Pressure Fluid pressure exerted by blood within glomerular capillaries Depends on Contraction of the heart Resistance to blood flow offered by afferent and efferent arterioles
More informationACR Meeting November, 2012
ACR Meeting November, 212 Arhalofenate is a Novel Dual-Acting Agent with Uricosuric and Anti-Inflammatory Properties Yun-Jung Choi, Vanina Larroca, Annette Lucman, Vic Vicena, Noe Abarca, Tim Rantz, Brian
More informationBUFFERING OF HYDROGEN LOAD
BUFFERING OF HYDROGEN LOAD 1. Extracellular space minutes 2. Intracellular space minutes to hours 3. Respiratory compensation 6 to 12 hours 4. Renal compensation hours, up to 2-3 days RENAL HYDROGEN SECRETION
More informationBIOLOGY - CLUTCH CH.44 - OSMOREGULATION AND EXCRETION.
!! www.clutchprep.com Osmoregulation regulation of solute balance and water loss to maintain homeostasis of water content Excretion process of eliminating waste from the body, like nitrogenous waste Kidney
More informationTherapeutics of Diuretics
(Last Updated: 08/22/2018) Created by: Socco, Samantha Therapeutics of Diuretics Thambi, M. (2017). The Clinical Use of Diuretics. Lecture presented at PHAR 503 Lecture in UIC College of Pharmacy, Chicago.
More informationChapter 19 The Urinary System Fluid and Electrolyte Balance
Chapter 19 The Urinary System Fluid and Electrolyte Balance Chapter Outline The Concept of Balance Water Balance Sodium Balance Potassium Balance Calcium Balance Interactions between Fluid and Electrolyte
More informationPRINCIPLES OF DIURETIC ACTIONS:
DIURETIC: A drug that increases excretion of solutes Increased urine volume is secondary All clinically useful diuretics act by blocking Na + reabsorption Has the highest EC to IC ratio = always more sodium
More informationUricosuric targets of tranilast
ORIGINAL ARTICLE Uricosuric targets of tranilast Asim K. Mandal 1, Adriana Mercado 2, Andria Foster 1, Kambiz Zandi-Nejad 3 & David B. Mount 1 1 Renal Divisions, VA Boston Healthcare System and Brigham
More informationPharmacokinetics of Drugs. Assistant Prof. Dr. Najlaa Saadi PhD Pharmacology Faculty of Pharmacy University of Philadelphia
Pharmacokinetics of Drugs Assistant Prof. Dr. Najlaa Saadi PhD Pharmacology Faculty of Pharmacy University of Philadelphia Absorption Is the transfer of a drug from its site of administration to the bloodstream.
More informationMS1 Physiology Review of Na+, K+, H + /HCO 3. /Acid-base, Ca+² and PO 4 physiology
MS1 Physiology Review of,, / /Acidbase, Ca+² and PO 4 physiology I. David Weiner, M.D. Professor of Medicine and Physiology University of Florida College of Medicine Basic principles Proximal tubule Majority
More informationThe kidneys are excretory and regulatory organs. By
exercise 9 Renal System Physiology Objectives 1. To define nephron, renal corpuscle, renal tubule, afferent arteriole, glomerular filtration, efferent arteriole, aldosterone, ADH, and reabsorption 2. To
More informationUrinary bladder provides a temporary storage reservoir for urine
Urinary System Organs Kidney Filters blood, allowing toxins, metabolic wastes, and excess ions to leave the body in urine Urinary bladder provides a temporary storage reservoir for urine Paired ureters
More information3/19/2009. The task of the kidney in acid-base balance Excretion of the daily acid load. Buffering of an acid load. A o B - + H + B - A o +OH - C +
The task of the kidney in acid-base balance Excretion of the daily acid load Buffering of an acid load Oxidation of amino acids, fats and carbohydrates often lead to acid production. On an average American
More informationA&P 2 CANALE T H E U R I N A R Y S Y S T E M
A&P 2 CANALE T H E U R I N A R Y S Y S T E M URINARY SYSTEM CONTRIBUTION TO HOMEOSTASIS Regulates body water levels Excess water taken in is excreted Output varies from 2-1/2 liter/day to 1 liter/hour
More informationOther Factors Affecting GFR. Chapter 25. After Filtration. Reabsorption and Secretion. 5 Functions of the PCT
Other Factors Affecting GFR Chapter 25 Part 2. Renal Physiology Nitric oxide vasodilator produced by the vascular endothelium Adenosine vasoconstrictor of renal vasculature Endothelin a powerful vasoconstrictor
More informationAcid Base Balance. Professor Dr. Raid M. H. Al-Salih. Clinical Chemistry Professor Dr. Raid M. H. Al-Salih
Acid Base Balance 1 HYDROGEN ION CONCENTRATION and CONCEPT OF ph Blood hydrogen ion concentration (abbreviated [H + ]) is maintained within tight limits in health, with the normal concentration being between
More informationRenal Function. 1. Glomerular filtration 2. Active tubular secretion 3. Passive tubular reabsorption 4. Excretion
59-291 Section 1, Lecture 5 Drug Excretion -most drugs are excreted in urine either as unchanged or drug metabolites Renal Function 1. Glomerular filtration 2. Active tubular secretion 3. Passive tubular
More information