Divergent effects of bombesin and bethanechol on stimulated gastric secretion in duodenal ulcer and in normal men.

To further investigate differences in the responses of normals and patients with duodenal ulcer with respect to gastrin release and acid and pepsin secretion, we infused bombesin (1 microgram/kg X h) or bethanechol (40 micrograms/kg X h) during the middle hour of a 3-h infusion of pentagastrin and compared the results with a pentagastrin infusion without added drug. Pentagastrin dosage (0.1 microgram/kg X h) was set to give about half-maximal response, to detect either inhibition or further stimulation of gastric secretion, whereas the dose of bombesin was chosen to give maximal gastrin but less than maximal acid secretion. Serum gastrin and somatostatin were also measured. In all subjects tested, bethanechol produced no effects on acid, gastrin, or somatostatin release but increased pepsin output. By contrast, bombesin inhibited pentagastrin-stimulated acid output in all 6 normal men by an average of 55%, whereas it inhibited acid output in only 2 of the 9 men with duodenal ulcer. Serum gastrin increases after bombesin in duodenal ulcer were three to four times greater than in normals. Although bombesin stimulates acid only by releasing gastrin, we postulate that bombesin may also simultaneously limit acid and pepsin secretion and speculate that this effect could be mediated by bombesin-induced somatostatin release. The cause for differences between duodenal ulcer and normal remain speculative.