Consecutive phases of gastric acid response to secretin in rats with chronic hypergastrinemia.

Secretin is known to inhibit gastric acid secretion but in some cases is able to stimulate both gastrin release and acid output. Different studies suggest that gastrin concentration at the parietal cell level modulates the acid response to secretin. Our purpose was to investigate in rats with chronic endogenous hypergastrinemia, as well as in control rats, the effect of an intravenous bolus of secretin GIH (from 0.25 to 4 clinical units (CU)/rat) on acid secretion. Both groups of rats were equipped with a chronic double gastric fistula allowing the collection of diluted gastric secretion every 2 min. We observed a dose-related inhibition of acid output (ID 50 less than 0.5 CU/rat) by secretin. In addition, in rats with hypergastrinemia; the acid response was phasic: an initial increase of acid output forewent its inhibition by 4 CU secretin. This phasic response suggests that secretin could act on acid secretion by releasing mediators which stimulate (as gastrin) and/or inhibit (as somatostatin) acid output.