AJP - Gastrointestinal and Liver Physiology, Vol 254, Issue 3 361-G365, Copyright © 1988 by American Physiological Society
Effect of bombesin and gastrin-releasing peptide on canine sphincter of Oddi
C. E. Sievert Jr, T. J. Potter, A. S. Levine, J. E. Morley, S. E. Silvis and J. A. Vennes
Gastroenterology Department, Veterans Administration Medical Center, Minneapolis, Minnesota 55417.
This study reports the effects of bombesin and gastrin-releasing peptide
(GRP) on the canine sphincter of Oddi using a method that allows repeated
cannulation of the biliary sphincter in the unanesthetized animal through a
Thomas cannula placed opposite the biliary papilla. Immediately after
intravenous administration of bombesin or GRP, phasic sphincter
contractions disappeared, basal sphincter pressures fell, and common bile
duct pressures rose. Because bombesin releases cholecystokinin (CCK) and
CCK resulted in a similar pattern to that of bombesin, the bombesin effect
on the sphincter of Oddi may have been secondary to CCK's effect on the
sphincter. To test if the bombesin effect on the sphincter of Oddi was due
to the release of CCK, we blocked CCK release by administration of
somatostatin, having first established that somatostatin blocked endogenous
CCK release in our animal model by use of an intraduodenal infusion of
lipid. Exogenous administration of bombesin failed to alter sphincter of
Oddi or common bile duct pressures in dogs treated with somatostatin.
Somatostatin did not, however, block CCK's effect on gallbladder
contraction, since exogenous administration of CCK after somatostatin
injection resulted in the pressure changes in the biliary tree typical of
CCK-induced gallbladder contraction. Thus bombesin administration appears
to result in sphincter relaxation and gallbladder contraction by the
release of endogenous CCK rather than by a direct effect. The increase in
common bile duct pressures was due to gallbladder contraction, since this
rise in pressure was abolished by cholecystectomy. The peptide effect on
sphincter contraction and basal sphincter pressure were unaffected by
cholecystectomy.
