Comparison of exogenous secretin and duodenal acidification of pepsin secretion in dogs

Gastric chief cells: receptors and signal-transduction mechanisms

Elucidation of receptors and mediators regulating gastric pepsinogen secretion has lagged behind understanding of the factors that control acid secretion. During the past decade, as a consequence of the development of in vitro models for studying the control of pepsinogen secretion at the cellular level, much information about chief cell receptors and signal-transduction mechanisms has been obtained, including the identification and characterization of receptors for secretin, vasoactive intestinal polypeptide, cholinergic agonists, gastrin, cholecystokinin, peptide YY, and cholera toxin. Moreover, these cell preparations have permitted secretagogue-induced changes in chief-cell calcium concentration, protein kinase C distribution, and phosphoinositide and cyclic nucleotide content to be measured and related to changes in pepsinogen secretion. This article reviews these advances, discusses areas of uncertainty and controversy, and indicates areas for future investigation.

Fine-morphology of chief cells in human gastric mucosa after secretin

Quantitative ultrastructural studies of human gastric mucosal chief cells during secretory stimulation have not been reported previously. In five healthy subjects we studied the effect of intravenous administration of 2 CU/kg of GIH secretin on gastric chief-cell ultrastructure. Gastric biopsies for quantitative ultrastructural analysis were obtained before and 15 and 30 min after secretin administration. Electron micrographs of 150 chief cells were analyzed by the Loud quantitative method. After secretin administration the percentage area occupied by zymogen granules decreased significantly at 15 and 30 min. At corresponding times membrane profile concentration (rough endoplasmic reticulum) increased significantly over basal values. This study provides morphological evidence of increased activity of chief cells after secretin administration.

Comparison of vasoactive intestinal peptide (VIP) and secretin in gastric secretion and mucosal blood flow

VIP and secretin were compared in regard to their effects on gastric acid and pepsin secretion induced by pentagastrin histamine or a peptone meal as well as on gastric mucosal blood flow and meal induced serum gastrin level in conscious dogs provided with gastric fistulas and denervated fundic pouches. Both VIP and secretin caused a dose-related stimulation of basal pepsin outputs and inhibition of pentagastrin-induced acid secretion. VIP, like secretin, inhibited pentagastrin and meal-induced gastric acid secretion but in contrast to secretin it caused inhibition of acid response to histamine. Inhibition of acid secretion by VIP or secretin was accompanied by secondary reduction in gastric mucosal blood flow in tests with pentagastrin or histamine and by depression of the serum gastrin level in tests with a peptone meal. This study indicates that in comparison with secretin, VIP has a wider spectrum of inhibition of stimulated gastric secretion and may be considered as one of the enterogastrones released in the small intestine.