AJP - Gastrointestinal and Liver Physiology, Vol 244, Issue 6 652-G655, Copyright © 1983 by American Physiological Society
Bombesin-induced tachyphylaxis markedly enhances gastrin response to a meal
T. Larson, J. Sanchez and I. L. Taylor
This study was designed to determine whether a bombesinlike peptide
mediated the gastrin response to food. Tachyphylaxis of gastrin release was
induced in six dogs by prolonged infusion of bombesin (500 ng X kg-1 X h-1)
before ingestion of a meal. An impaired postprandial gastrin response
during bombesin tachyphylaxis would be indirect evidence that a
bombesinlike peptide mediated the gastrin response to food. Serum gastrin
concentrations peaked (74 +/- 18 pM) 1 h after commencement of the bombesin
infusion and then fell significantly (P less than 0.01), reaching a nadir
of 15 +/- 1 pM at 4 h. Dogs were then fed the standard meal (15 g/kg Prime
dog food), and the serum gastrin response was compared with that observed
in response to the meal ingested during saline infusion. There was sixfold
enhancement (P less than 0.01) of meal-stimulated gastrin release during
bombesin infusion compared with saline infusion. Stopping the bombesin
infusion before ingestion of the meal still resulted in significant (P less
than 0.05) enhancement of the meal response. Although pancreatic
polypeptide responses to bombesin also exhibited tachyphylaxis, prolonged
infusion of bombesin did not enhance the pancreatic polypeptide response to
food. We conclude that a bombesinlike peptide does not mediate the gastrin
response to food in dog. We speculate that bombesin stimulates both
secretion and synthesis of gastrin but that only secretion is subject to
tachyphylaxis. The enlarged secretory pool produces an enhanced response
when the G cell is exposed to stimulants other than bombesin.
