Effect of calcitonin on bombesin-stimulated gastric acid secretion in patients with duodenal ulcer.

Intravenous infusion of bombesin (0.9 micrograms/kg/hour) caused a significant increase in gastric acid secretion and serum gastrin concentration in 8 duodenal ulcer patients. Intravenous infusion of calcitonin (2 MRCU/kg/hour) produced a significant decrease in gastric acid output and in integrated gastrin output produced by bombesin infusion (0.9 micrograms/kg/hour) in the same 8 patients with duodenal ulcer. Percentage of inhibition was 49.7 and 40.8, respectively. Simultaneous infusion of calcitonin and bombesin caused no significant difference in serum calcium concentration. It is suggested that the inhibitory effect of calcitonin on acid secretion elicited by bombesin is produced, at least in part, by a fall in serum gastrin caused by bombesin. In addition, calcitonin might directly inhibit the parietal cells by releasing endogenous gastric somatostatin.