Aminopyrine accumulation of isolated parietal cells from the rat stomach. Effect of histamine and interaction with endogenous inhibitors.

The inhibitory properties of secretin, vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), somatostatin and prostaglandin E2 (PGE2) on acid production in response to histamine were tested in vitro by measuring the 14C-aminopyrine (14C-AP) uptake into isolated rat parietal cells, a reliable index of H+ generation. All compounds significantly inhibited 14C-AP accumulation and 4 X 10(-8) mol/l secretin, 7 X 10(-8) mol/l PGE2 and 2 X 10(-7) mol/l CCK decreased the effect of 10(-4) mol/l histamine by 50% (IC50). VIP and somatostatin did not reduce AP-uptake to such extent and the approximate IC50 values could not be established. The type of inhibition by all peptides and PGE2 appeared not to be competitive in nature. Our data suggest that these compounds inhibit acid production by a mechanism localized directly at the parietal cell and that secretin and CCK are unlikely to exert a physiological role as inhibitors of gastric acid secretion.