[Is forskolin a stimulant of gastric secretion?]

The diterpene, forskolin, direct activator of the catalytic subunit of the adenylate cyclase from various tissues, also stimulates gastric acid secretion: in vitro, with an isolated parietal cell preparation, forskolin dose-dependently stimulated acid secretion (EC50: 1 microM) (measured by accumulation in the acidic spaces of the weak base [14C]-aminopyrine) and the maximal acid secretory value at 0.1 mM was 4 times higher than that obtained with histamine. Forskolin dramatically increased the production of intracellular cyclic-AMP at a level 4 times higher than that obtained with histamine at the same concentration. In vivo, gastric acid secretion of the rat is dose-dependently increased. The doses required to get a significant response (100 nmol/kg) were 1,000 times higher than those required for gastrin and 100 times lower than those for histamine, but the same maximal value was obtained. Cimetidine did not significantly modified this response. These results demonstrate that, both in vitro and in vivo, forskolin is a potent stimulant for gastric acid secretion.