Regulation of gastric acid secretion by secretin and serotonin

Gastric acid, calcium absorption, and their impact on bone health

Calcium balance is essential for a multitude of physiological processes, ranging from cell signaling to maintenance of bone health. Adequate intestinal absorption of calcium is a major factor for maintaining systemic calcium homeostasis. Recent observations indicate that a reduction of gastric acidity may impair effective calcium uptake through the intestine. This article reviews the physiology of gastric acid secretion, intestinal calcium absorption, and their respective neuroendocrine regulation and explores the physiological basis of a potential link between these individual systems.

Basal and histamine-induced gastric acid secretion in alloxan diabetic rats

1. Effects of alloxan-induced diabetes on the rat gastric acid secretion were investigated using a number of biostatistical models described earlier. 2. Histamine-induced gastric acid secretion was found to be decreased in alloxan-diabetic rats when compared with their age-matched controls. 3. Basal acid secretion was also decreased depending on experimentally-induced diabetes. 4. The above results strongly suggest that alloxan-induced diabetes depresses vagal activity and H2-receptor activity in the stomach.

The role of endogenous prostaglandins in hormone-stimulated pancreatic exocrine secretion

The authors have previously shown that neurotensin and secretin inhibit gastric acid secretion in the dog and that these actions are inhibited by the prostaglandin synthesis inhibitor indomethacin. Conversely, neurotensin and secretin share similar stimulatory effects on pancreatic exocrine secretion. In the present study, the effects of blockade of prostaglandin synthesis by indomethacin on neurotensin-, cholecystokinin-, and secretin-stimulated exocrine secretion are examined along with the effects of these same agents on the release of pancreatic polypeptide. The studies were performed on conscious dogs with chronic gastric and pancreatic cannulas. Dose-dependent increases in pancreatic exocrine secretion of water and bicarbonate were observed with IV infusion of neurotensin or secretin; however, inhibition of prostaglandin synthesis by indomethacin abolished this response. Protein secretion stimulated by either neurotensin or cholecystokinin was not affected by prostaglandin inhibition. Cholecystokinin and neurotensin infusion stimulated release of pancreatic polypeptide; only neurotensin-stimulated release of pancreatic polypeptide was inhibited by indomethacin treatment. It is concluded that intact prostaglandin synthesis is necessary for the actions of neurotensin and secretin (but not that of cholecystokinin) on pancreatic exocrine secretion of water and bicarbonate and for neurotensin- (but not cholecystokinin-) stimulated release of pancreatic polypeptide.

Biostatistical modeling of the effect of intravenous histamine-infusion on the rat gastric acid secretion

In this study, a variety of linear and nonlinear biostatistical models of regression were tested to evaluate the histamine-induced gastric acid secretion using the lumen-perfusion model in the rat. Among the linear, parabolic, and polynomial models tested, 3rd- and 4th-order polynomial models of regression exerted best correlations between the time and histamine-induced gastric acid secretion. In order to avoid undulatory behaviors in the regression curves, we conducted the polynomial regression analysis up to 5th order.

Influence of endogenous prostaglandins on secretin-mediated inhibition of gastric acid secretion in dogs

The influence of endogenous prostaglandins on secretin-mediated inhibition of gastric acid secretion was examined in 6 mongrel dogs with Thomas gastric and Herrera pancreatic cannulas. The dogs were given intravenous pentagastrin (1 microgram/kg.h) during the 180-min experiment, and graded doses of secretin (0.3-1.5 micrograms/kg.h) (1-5 CU/kg.h) were infused intravenously between 60 and 120 min. In alternate, otherwise identical experiments, a prostaglandin synthesis inhibitor, either indomethacin or meclofenamate, was also administered throughout the experiment. Increasing doses of secretin led to increasing inhibition of gastric acid output with the maximum inhibition at 1 microgram/kg.h (3.3 CU/kg.h) of secretin. Both indomethacin and meclofenamate abolished the inhibitory effects of secretin on gastric acid secretion. The inhibitors of prostaglandin generation had no effect on the serotonin system. We concluded that secretin mediates its inhibitory action on gastric acid secretion, at least in part, through endogenous prostaglandins.

Peptide YY interacts with secretin and duodenal acidification to inhibit gastric acid secretion

Previous studies have indicated that plasma levels of peptide YY (PYY) increase significantly after a meal. The purpose of this study was to characterize the interaction of PYY and secretin in the inhibition of gastric acid secretion, and to determine whether PYY can influence acid-induced inhibition of gastric acid secretion in conscious dogs. I.v. administration of PYY at 200 pmol/kg/h inhibited pentagastrin (1 microgram/kg/h)-stimulated gastric acid output (P less than 0.05). PYY further augmented i.v. secretin-induced inhibition of pentagastrin-stimulated gastric acid output by 32 +/- 7%, and intraduodenal hydrochloric acid-induced inhibition of pentagastrin-stimulated gastric acid output by 40 +/- 12%. The mean integrated release of secretin response to duodenal acidification (3.9 +/- 1.0 ng-[0-60] min/ml) was not affected by PYY (3.3 +/- 0.9 ng-[0-60] min/ml). The present study demonstrates that PYY can interact with secretin and duodenal acidification in an additive fashion to inhibit pentagastrin-stimulated gastric acid secretion. Our results suggest that several hormones that are released postprandially can interact with each other to inhibit gastric acid secretion.