Activation of human adenylate cyclase in the upper gastrointestinal tract by vasoactive intestinal polypeptide.

The effects of various polypeptide hormones known to inhibit gastric acid secretion were tested on the adenylate cyclase system in human gastric and duodenal mucosal homogenates. Glucagon and secretin failed to stimulate the enzyme system in the stomach. The latter hormone produced a small but significant activation of the duodenal cyclase. The vasoactive intestinal polypeptide (VIP), however, induced a dose-dependent increase of enzyme activity throughout the stomach and the duodenum. Maximal effects (1.8 to 3.0-fold increase) were observed at a VIP-concentration of about 10 microgram per ml. Because the entire physiological role of VIP in gastric function has not been defined, ipt cannot be discerned whether the VIP-stimulated adenylate cyclase is linked to inhibition of gastric acid secretion or to another as yet unrecognized effect of this hormone in human gastric function.