Clinical Chemistry (CHE221) Professor Hicks Lecture 15. Bilirubin and Cholesterol

Transcription

1 linical hemistry (E221) Professor icks Lecture 15 Bilirubin and holesterol opyright 2009 harles icks like dissolves like fats, oils, grease, contain lots of nonpolar bonds water is a polar substance polar and nonpolar substances are not soluble in each other polar substances will dissolve in other polar substances nonpolar substances will dissolve in other nonpolar substances oil water opyright 2009 harles icks surfactants soaps, detergents, phospholipids all said to be amphiphilic polar head group O 2 OPO 3 2 OSO 3 nonpolar chain polar and nonpolar regions O O different ways to represent the same structure O O opyright 2009 harles icks 1

2 micelles form when using soap with water polar head groups point out facing solvent water nonpolar tails point in oils (dirt) dissolve in the nonpolar interior liposomes double layer formed polar faces inside and out forms spontaneously resemble cell membrane micelle liposome opyright 2009 harles icks a steroid alcohol rigid structurally a critical component of cell membranes provides fluidity amphiphilic molecule O group faces water, regions in membrane not digested to O O basic steroid structure opyright 2009 harles icks bile acids cholic acid made up of oxidized forms of such as cholic acid amphiphilic molecules play roles aiding absorption of fats and fat soluble vitamins opyright 2009 harles icks 2

3 steroid hormones hormones derived from the same 4 ring structure as Glucocorticoids mediate inflammation and immune response Mineralocorticoids involved in Na +, K + absorption/excretion in kidneys Estrogen female sex hormone Testosterone male sex hormone opyright 2009 harles icks bilirubin two forms: unconjugated bilirubin carboxylic acids not derivatized to esters not soluble in water unconjugated bilirubin esterification (twice) conjugated bilirububin form of bilirubin with two ester groups soluble in water opyright 2009 harles icks conjugated bilirubin direct vs indirect bilirubin unconjugated conjugated occurs in liver unconjugated form transported bound to albumin in early methods such as the Van den Bergh method only the conjugated form was detected in first step since the was reaction was run in water this is the direct bilirubin (conjugated form) reagent is then added to dissolve nonpolar compounds and unconjugated form dissolves and reacts to produce more color change this is the indirect bilirubin (unconjugated form) opyright 2009 harles icks 3

4 measurement of bilirubin in infants no lipochromes to interfere with absorbance lipochromes visible absorbing substances such as carotenoids infant serum analyzed by measurement of absorbance of bilirubin itself at 455 nm hemolysis which is common in infants can be corrected for by subtracting blank opyright 2009 harles icks bilirubin metabolism Prehepatic epatic conjugation occurs in liver Postepatic opyright 2009 harles icks jaundice aka icterus 1) Prehepatic 2) epatic conjugation occurs in liver 3) Postepatic opyright 2009 harles icks 4

5 jaundice 1) prehepatic jaundice high levels into liver hemolytic anemia unconjugated hyperbilirubinemia as high as 5 mg/dl rate liver can conjugate it is limiting not elevated in urine since not filtered by kidneys when bound to albumin opyright 2009 harles icks jaundice 2) hepatic jaundice most common of 3 types jaundice Gilbert syndrome most common hepatic jaundice deficiency in absorption by liver prevents conjugation elevated unconjugated bilirubin but still below 3 mg/dl opyright 2009 harles icks jaundice 3) posthepatic jaundice accumulation of bile due to decreased excretion caused by mechanical obstruction of bile flow from liver to intestines conjugated bilirubin rises in serum stool loses dark color urine level conjugated bilirubin rise opyright 2009 harles icks 5