EFFECTS OF NICOTINE ON GASTROINTESTINAL SECRETIONS

Transcription

1 GASTRONTROLOGY 1971 by The Williams & Wilkins Co. Vol. 60, No.6 Printed in U. S. A. FFCTS OF NCOTN ON GASTRONTSTNAL SCRTONS STANSLAW J. KONTURK, M.D., TRAVS. SOLOMON, W. GORG MCCRGHT, LONARD R. JOHNSON, PH.D., AND UGN D. JACOBSON, M.D. Department of Physiology and Biophysics, University of Oklahoma Medical Center, Oklahoma City, Oklahoma The effect of nicotine on gastric, pancreatic, and hepatic exocrine secretions was assessed in conscious dogs prepared with various combinations of Heidenhain pouch, gastric, pancreatic, and biliary fistulas. The alkaloid was infused in doses corresponding to amounts absorbed from smoking up to four cigarettes in 1 hr. n the pancreas, nicotine inhibited the secretin-stimulated secretion of both fluid and bicarbonate, and the degree of inhibition was dose-related. Spontaneous biliary secretion of bicarbonate was also depressed by the drug. Nicotine did not alter gastric secretion of acid, gastric mucosal blood flow, or the mucosal barrier to hydrogen or sodium ions. These findings provide a possible link between cigarette smoking and duodenal ulcer formation. Specifically, the nicotine from cigarette smoke may inhibit pancreatic and hepatic bicarbonate secretion in man, thereby depriving the duodenum of the alkaline secretion it needs to neutralize gastric acid adequately. Cigarette smokers are known to have a higher incidence of duodenal ulcer than nonsmokers, but the association between smoking and ulcers has not been considered to be one of cause and effect. Rather, the personality characteristics which lead these individuals to smoke have been thought to predispose them to ulcer formation. This reasoning is based on (1) statistical inferences from duodenal ulcer incidence among smokers versus nonsmokers, 1 and (2) lack of laboratory evidence that any component of Received November 13, Accepted January 19, Address requests for reprints to: Dr. ugene D. Jacobson, Department of Physiology and Biophysics, University of Oklahoma Medical Center, 800 N.. 13th Street, Oklahoma City, Oklahoma This study was aided by a grant from the American Medical Association ducation and Research Foundation. The authors wish to express appreciation to Mrs. Louise Wyss and Mr. Alvin C. K. Chang for technical assistance, to Dr. Thomas Robitscher of Ayerst Laboratories for supplying the pentagastrin (Peptavlon), and to Dr. Morton. Grossman for the gift of porcine gastrin used in our experiments. cigarette smoke affects a mechanism which, if disturbed, could promote ulcer formation (e.g., increased gastric acid secretion). 2-5 Nicotine in tobacco smoke is absorbed into the circulation in known amounts with each cigarette smoked. 6 f nicotine were ulcerogenic in the duodenum, a likely alteration would involve maintenance of an abnormally acid milieu in the lumen of the gut. xcessive duodenal acidity could be caused by increased acid secretion from the stomach, or by decreased formation of the major neutralizer of duodenal acid, i.e., bicarbonate secreted by the pancreas and liver. To determine whether cigarette smoking might thus contribute to the formation of duodenal ulcer, we designed experiments to determine what role, if any, nicotine plays in the production of excessive duodenal acidity. Specifically, the effects of nicotine on gastric, pancreatic, and hepatic secretions were studied in conscious dogs. Methods Three groups of adult mongrel dogs, weighing 15 to 21 kg each, were used for studies of (1) gas- 1098

2 June 1971 NCOTN AND BCARBONAT SCRTON 1099 tric secretion (6 dogs), (2) pancreatic secretion (4 dogs), and (3) biliary secretion (2 dogs). xperiments on a given group of animals were conducted on alternate days, and no more often than three times per week. Before each experiment, food but not water was withheld from the dogs for 18 to 20 hr. The differences in gastric, pancreatic, and biliary secretion before and after nicotine administration were determined by Student's t-test or by the Mann-Whitney U test. 7 As used in the text, significance indicates P < Gastric secretory studies. Three dogs were prepared surgically with a Heidenhain pouch (HP) and gastric fistula (GF) for use in gastric secretory and mucosal barrier studies. Musocal blood flow was measured in 3 other dogs prepared with only GF. Secretory studies were begun 3 weeks following surgery. Secretion was collected from the HP and GF every 15 min; the volume was recorded, and titratable acidity (end point, ph 7.0) measured with 0.2 N NaOH using an autoburette titrator and ph meter (Radiometer, Copenhagen). Throughout each experiment, 0.15 M NaC was infused intravenously at 40 ml per hr from a calibrated peristaltic pump (Harvard Apparatus Company, Millis, Mass.). Fifteen minutes after saline was begun, pentagastrin or histamine was infused in a dose evoking about half-maximal gastric acid output. Secretagogue infusion was continued for the next 3 v" hr. Ninety minutes after pentagastrin or histamine was started and the gastric secretory rate was relatively stable, nicotine (J. T. Baker Chemical Company, Phillipsburg, N. J.) was added to the intravenous infusion in a dose of 100 f.lg per kg of body weight for 1 hr only. This dose of nicotine corresponds to the amount absorbed through the lungs by a man smoking four cigarettes. 6 The effect of nicotine on basal gastric acid secretion was determined in dogs in which saline alone was infused for the hr test period. Nicotine was added to the saline infusion for a 1-hr period, starting 105 min after the test was begun. n control studies on the same animals, either pentagastrin or histamine without nicotine was infused throughout the experimental period. The gastric mucosal barrier was examined in the oxyntic gland area of the HP. The pouch was first washed thoroughly with 0.1 N HC and emptied. Another 40 ml of this solution were instilled via a vertical glass reservoir attached to the metal cannula of the pouch by a rubber tube. 8 During the 15-min observation period, the contents of the pouch were mixed by pouch contractions. Fourteen successive 15-min observation periods were made in each experiment. At the end of each period, the pouch was drained completely, the volume recovered was recorded, and the samples were saved for analysis. Concentration of acid was determined by electrometric titration of the sample. Sodium and potassium were measured using a standard flame photometer. The quantities of acid, sodium, and potassium entering or leaving the pouch during the 15-min periods were calculated as the difference between the instilled and recovered amounts (volume X concentration). By convention, net losses from the pouch were reported as negative values and net gains as positive values. n 5 G F dogs, aminopyrine clearance was used to measure mucosal blood flow. 9 An initial loading dose of aminopyrine (20 mg per kg) was injected rapidly into a leg vein and followed by a maintenance dose (5 mg per kg-hr) infused intravenously in 0.15 M NaC for the remainder of the experiment. The concentrations of aminopyrine in plasma and in gastric juice samples were determined spectrophotometrically.'o ither histamine (1 mg base per hr) or extracted porcine gastrin (20 g per hr) was infused with the aminopyrine. After the experiment was under way for 2 hr, nicotine (50 f.lg per kg) was infused for 1 hr. Average mucosal blood flow values for the last two 15-min periods of the hour with nicotine were compared with the corresponding periods in the hour before nicotine was administered. Pancreatic secretory studies. A second group of animals (4 dogs) was prepared with a GF and pancreatic fistula (PF). 12 Pancreatic secretory studies were started 4 weeks after the surgery. Throughout the test, the GF was left open to allow drainage of gastric juice to the outside. very 15 min, pancreatic secretion was collected and the volume recorded to the nearest 0.2 m!. The bicarbonate concentration in pancreatic secretion was measured by adding 0.5-ml samples of pancreatic juice to 1.0 ml of 0.1 N HC, heating the mixture to a brief boil, cooling, and backtitrating the excess acid to ph 7.0 with the autoburette titrator. Basal pancreatic secretion was collected for 15 min before each experiment. f the volume of juice did not exceed 2.0 ml, the test was begun. n each experiment, 0.15 M NaC was intravenously infused at a constant rate of 40 ml per hr by a peristaltic pump. After the basal collection, purified natural secretin (Gastrointestinal Hormone Laboratory, Karolinska nstitutet, Stockholm, Sweden) was added to the infusion in a dose of 1.5 U per kg-hr. This dose of secretin evokes near-maximal pancreatic volume and bicarbonate secretion. When pancreatic secretion had become relatively stable (90 min after

3 1100 KONTURK T AL. Vol. 60, No.6 c: ' LO.:::::. 0- W Heidenhaln Pouch PNTAGASTRN or HSTAMN!NCOTN OO)lQ/kg-hr 1 J ' 1 / 1, + + ~ / t - t ~,( 1 PentaQastrin FG. 1. The effect of nicotine (100 f,lg per kg-hr) on acid output from Heidenhain pouches of dogs stimulated by pentagastrin (2 f,lg per kg-hr) or histamine (40 f,lg per kg-hr). ach point on the line represents the mean value from six experiments on 3 dogs with gastric fistulas and Heidenhain pouches. Vertical bars represent standard errors of the mean. PNTAGASTRN or HSTAMN 1 NCOTN OOJ,Q/kQ-hr 1 c: '!Q."- 0- W 6 4 Gastric Fistula 6-._.- Basal 2 _ PentaQastrin <>- - - Histamine FG. 2. The effect of nicotine on basal gastric acid secretion and pentagastrin-induced secretion from the gastric fistula. ach point on the line represents the mean value from six experiments on 3 dogs with gastric fistulas and Heidenhain pouches. Vertical bars represent standard errors of the mean. the start of secretin infusion), nicotine was infused for 60 min in a dose of 12.5, 25, 50, or 100 J,lg per kg. Attempts to use higher doses of nicotine failed because the animals became restless, retched, and salivated. Biliary secretory studies. The gallbladder was excised and the minor pancreatic duct ligated in 2 dogs which had previously been prepared with a GF. A Thomas cannula was placed in the duodenum opposite the opening of the common bile

4 June 1971 NCOTN AND BCARBONAT SCRTON 1101 duct. Postoperatively the animals lost no weight and remained in good condition. xperiments were started about 2 weeks after the second operation. The GF was kept open during each experiment and gastric juice drained to the outside. The duodenal fistula was opened and the bile duct was cannulated using polyethylene tubing (ntramedic P 190, outside diameter 2.0 mm). Bile was collected by gravity drainage every 15 min. The volume was recorded and TABL 1. Net changes across Heidenhain pouches irrigated with HC solution before and during nicotine infusion a Solution P e r i ovolume d ~ W Na' K' ml "q "q #q Control mq HC/liter mq HC/liter ' nicotine, 100 Jlg/ kg hr mq HC/liter a Data represent mean values from two experiments each on 3 dogs. ach observation period lasted 15 min. 1 bicarbonate concentration was measured by the same method used for pancreatic juice. Throughout each experiment, 0.15 M NaC was intravenously infused from a peristaltic pump at 40 ml per hr. After 90 min of saline infusion, nicotine (100 J.tg per kg) was added to the infusion solution for the next hour, then saline alone. n control tests, saline was the only substance infused. Results Gastric secretory response. The intravenous administration of nicotine had no effect on half-maximal gastric acid secretion evoked by either pentagastrin or histamine TABL 2. Lack of effect of intravenously administered nicotine on gastric mucosal blood flole in 5 dogs 16th gastric fistula Dog no. Secretor.'; stimulant stima ted g a ~ t r i ( ' mu('oaa hlood flnw Control pt>riod 750 Histamine Histamine Histamine Histamine Gastrin Gastrin 69 SCRTN 1.5units/ko-hr ~ NCOTN 1 ~ k ( ) 1 i n e infusion (.'i0 # ~ /. hk r ~ ) m f/m ill c: 15 '!! ' JlO/kO-h. Nicotine e> )'O/ko-hr Nicotine )O/kO-hr Nicotine _ )lq/ko-hr Nicotine FG. 3. The inhibition of secretin-induced pancreatic secretion by four doses of nicotine (12.5 to 100 /i-g per kg-hrl in dogs with pancreatic fistulas. ach line is plotted from the mean values of two experiments on 4 dogs (i.e., eight experiments in all). Vertical bars represent standard errors of the mean.

5 1102 KONTURK T AL. Vol. 60, No SCRTN 1.5units/kg-hr NCOTN 1 20 c: e 10 ;:::: 1.5 '0' u :t: <:T 0.5 \ '-.t... J / ~ f \ / \- -f JlQ/kg-hr Nicotine JO/kcrhr Nicotine -._ Jl/kQ-hr Nicotine... _ )QkQ-hr Nicotine FG. 4. The inhibition of bicarbonate output in secretin-induced pancreatic secretion by four doses of nicotine (12.5 to 100!Lg per kg-hr). Vertical bars represent standard errors of the mean. Solu tion infused TABL 3. ffect of nicotine on bicarbonate concentration in pancreatic secretion Period a Bicarbonate concentration ll after nicotine dose of 12.5 ~~ /. k hg r 25 ~g /. k hr g 50 ~~ / k hr g 100 ~ ~ / kr g. h m q/liter Secretin, 1.5 U/kg-hr ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 1.5 Secretin + nicotine ± ± 1.5< 115 ± ± 2.7< ± 3.1< 104 ± 2.1< 108 ± 4.5< 107 ± 2. 3< ± 3.0< 99 ± 1. 9< 111 ± 3.4< 88 ± 4.4< ± 2.9< 99 ± 3.0< 105 ± 6.6< 98 ± 3.6< Secretin ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 1. 9 a ach observaton period lasted 15 mm. ach bicarbonate concentration represents the mean value of eight experiments performed in 4 dogs. C A significant difference (P < 0.05) from the last secretin control period (Mann-Whitney U test). in six experiments on 3 dogs with GF and HP (figs. 1 and 2). This was confirmed by comparing the response patterns from experiments using gastric stimulants and nicotine with those obtained in control experiments, in which no nicotine was given. Likewise, nicotine infusion failed to alter basal gastric acid output. futravenous nicotine had no effect upon net movement of water H +, Na +, and K + in HP irrigated with 100 mn Hel (table 1). Data obtained during nicotine infusion closely resembled control

6 June 1971 NCOTN AND BCARBONAT SCRTON 1103 values, except that the concentration of acid in fluid recovered from the pouch was slightly lower during the control periods. n all experiments, net changes in sodium and potassium transport were negligible. n a few additional experiments, nicotine was included in the irrigating solution to permit.= 10 " NCOTN 1000Q/kQ-hr 1 topical contact between the alkaloid and the mucosal barrier. Again, we observed no significant alteration in net movement of fluid and electrolytes. n the 3 dogs with GF alone, nicotine administration brought about no consistent alterations in gastric mucosal blood flow Control ~ - - t - - t - - f _, Nicotine * t FG. 5. The effect of nicotine (100 lg per kg-hrl on spontaneous hepatic bile flow. ach line is plotted from the mean values of four experiments on 2 dogs (i.e., eight experiments in all). Vertical bars represent standard errors of the mean. 80 c:: 10 " 60 ~ <.> :: e- W 40 ~ NCOTN OO}lQ/kQ-hr 20 Nicotine FG. 6. The effect of nicotine on bicarbonate content of spontaneous hepatic bile flow. Vertical bars represent standard errors of the mean.

7 1104 KONTURK T AL. VoL. 60, No.6 during stimulation of the stomach with gastrin or histamine (table 2). Pancreatic secretory response. The pancreatic response to secretin stimulation reached a peak about 45 min after the start of infusion, with both volume flow and bicarbonate output remaining stable during the rest of the control period. Nicotine in doses ranging from 12.5 to 100,.,.g per kg-hr then caused a statistically significant inhibition of both flow rate and bicarbonate output (figs. 3 and 4). The bicarbonate concentration in pancreatic juice began to drop about 15 min after the start of nicotine infusion and continued to decrease during most ofthe infusion period (table 3). Volume flow was usually depressed about 30 min after the start of nicotine infusion. Maximal inhibition of flow rate and bicarbonate output were apparent at the end of the nicotine infusion. Maximal inhibition of bicarbonate output was 23% with the 12.5,.,.g per kg dose of nicotine, 41 % with the 25-,.,.g dose, 54% with the 50-,.,.g dose, and 62% with the 100-,.,.g dose. mmediately after cessation of the nicotine infusion, volume and bicarbonate output rose quickly, often exceeding the prenicotine levels. Biliary secretory response. When nocitine was infused in a dose of 100,.,.g per kg-hr, both the volume and bicarbonate output of unstimulated hepatic bile decreased by about 50% (figs. 5 and 6). Upon withdrawal of the nicotine, biliary secretion quickly returned to the prenicotine level. Discussion Nicotine depressed pancreatic and hepatic secretion of bicarbonate without affecting processes related to gastric secretion of acid. The dosage range of intravenously infused nicotine that inhibited brisk pancreatic secretion in our dogs was equivalent to the amount of nicotine absorbed in 1 hr when a man smokes one-half to four cigarettes (12.5 to 100,.,.g per kg).6 Although our findings are limited by experimental conditions (i.e., use of the conscious dog and short term infusion of the alkaloid), the results suggest a possible mechanism whereby cigarette smoking could promote duodenal ulcer formation. f species differences and the brevity of infusion are not major factors, the inhibition of glandular bicarbonate production by nicotine would lead to a hyperacidic condition in the upper gut of man. Failure of the stomach to respond to nicotine may depend upond the duration of exposure to the alkaloid. Our finding that short term administration of nicotine did not alter gastric secretory rate and mucosal blood flow agrees with results reported by others who have used different preparations Recently, however, long term administration of nicotine was shown to increase secretory responsiveness in the rat stomach. 13 The mechanism whereby nicotine depresses pancreatic and biliary production of bicarbonate remains unclear. n 1909 dmunds 14 showed that nicotine inhibited pancreatic secretion stimulated by secretin, and he proposed that the effect was mediated by adrenalin. However, the amounts of nicotine used were enormous and evoked marked respiratory distress and large pressor responses in the anesthetized dog. Our conscious animals exhibited no respiratory response to nicotine. Simple competition between nicotine and acetylcholine for a cholinergic receptor might be implicated. However, vagotomy has been shown to augment the pancreatic secretory response to secretin, 15 and atropine-induced inhibition of the secretin-stimulated pancreas is not associated with a decline in bicarbonate concentration of the juice. 16 Nicotine could act directly on enzymatic reactions responsible for bicarbonate production or could involve intermediaries which alter gastrointestinal secretions. Nicotine has been reported to release corticosteroids, 17 5-hydroxytryptamine, 18 catecholamines,1 9 and gastrin, 20 but these agents in large quantities alter gastric secretion-an effect we did not observe with nicotine. RFRNCS 1. Monson RR: Cigarette smoking and body form in peptic ulcer. Gastroenterology 58: , Odori Y, Magee DF: The action of some agents active at autonomic ganglionic sites on the secretory response of the Heidenhain pouch to various stimuli. urop J Pharmacol 8: , 1969

8 June 1971 NCOTN AND BCARBONAT SCRTON nos 3. Nakajima S: Action of nicotine on H + secretion, potential, and resistance in isolated bullfrog gastric mucosa. Proc Soc xp Bioi Med 133: , Thompson JH: ffects of nicotine and tobacco smoke on gastric secretion in rats with gastric fistulas. Dig Dis 15: , Naitove A, Constantian MB, Arkins T : Gastric hemodynamics effects of smoking and nicotine. Gastroenterology 58:1058, Kuhn H : Tobacco alkaloids and their pyrolysis products in the smoke, Tobacco Alkaloids and Related Compounds. dited by US von uler. New York, The Macmillan Company, 1965, p Siegel S: Nonparametric statistics from the behavioral sciences. McGraw-Hill Book Company, nc, New York, Bloom DS, Jacobson D, Grossman M: Validation of dilution indicators in the stomach. Gastroenterology 52: , Swan KG, Jacobson D: Gastric secretion and blood flow in conscious dogs. Arner J Physiol 212: , Brodie BB, Axelrod J: The fate of aminopyrine (Pyramidon) in man and the methods for estimation of aminopyrine and its metabolites in biological material. J Pharmacol xp Ther 99: , Gregory RA, Tracy HJ: The constitution and properties of two gastrins extracted from hog antral mucosa. Gut 5: , Stening GF: A modification of a chronic pancreatic fistula in the dog. Brit J Surg 56: , Thompson JH, Angulo M: Chronic effects of nicotine on rat gastric secretion. xperientia 26: , dmunds CW: The antagonism of the adrenal glands against the pancreas..j Pharmacol xp Ther 1: , Moreland HJ, Johnson LR: ffect of vagotomy on pancreatic secretion stimulated by endogenous and exogenous secretin. Gastroenterology 60: , Konturek SJ, Tasler J, Obtulowicz W: ffect of atropine on pancreatic responses to exogenous and endogenous secret ins. Arner J Dig Dis (in press) 17. Kershbaum A, Pappajohn DJ, Bellet S, et al: ffect of smoking and nicotine on adrenocortical secretion. JAM A 203: , Burks TF, Long JP: Release of 5-hydroxytryptamine from isolated dog intestine by nicotine. Brit J Pharmacol Chern 30: , Westfall TC: Tobacco alkaloids and the release of catecholamines, Tobacco Alkaloids and Related Compounds. dited by US von uler. New York, The Macmillan Company, 1965, p Olbe L, lwin C: ffects of tobacco smoking and nicotine on gastric acid secretion in dogs, Tobacco Alkaloids and Related Compounds. dited by US von uler, New York, The Macmillan Company, 1965, p