A Comparison with Other Secretagogues

on cyclic AMP levels in the presence of 5 mM theophylline. By contrast, caerulein and secretin increased cyclic AMP levels by 27 and 208%, respectively. Bombesin, bombesin-NP, and litorin did not activate adenylate cyclase in a purified pancreatic plasma membrane preparation, whereas caerulein and secretin increased this activity 20 and 16-times, respectively. Calcium efflux was estimated in isolated acinar cells from the rat pancreas. The concentration of bombesin, bombesin-NP, litorin, caerulein, the C-terminal octapeptide of cholecystokinin-pancreozymin, and carbamylcholine that produced half-maximal stimulation of calcium efflux were 0.30 nM, 0.50 nM, 2.00 nM, 0.80 nM, 0.20 nM, and 3.00 uM, respectively. Maximal stimulation of calcium efflux by bombesin or C-terminal octapeptide of cholecystokinin-pancreozymin lasted only 10 min. In Part of this work has been presented in abstract form in 1975. Arch. I,lt. Physiol. Biochiin. 83: 993-994. Received for ptiblication 29 January 1976 and in revised form 7 June 1976. addition, refractoriness to a new addition of bombesin was observed after 1 h preincubation with bombesin. In conclusion, amylase secretion and calcium efflux from the rat pancreas are stimulated in vitro by peptides of the bombesin family.