Effects of gastrointestinal hormones on ileal vascular and visceral smooth muscle

Blood levels of gastrin, secretin, gastric inhibitory polypeptide (GIP), and cholecystokinin octapeptide (CCK-8) increase after a meal and may affect vascular and/or visceral smooth muscle. To study this possibility, we measured the effects of local intra-arterial infusion of these hormones on ileal perfusion pressure and intestinal wall compliance. In pentobarbital sodium-anesthetized dogs, a segment of ileum was exteriorized and vascularly perfused at constant flow with arterial blood. Wall compliance was calculated from the pressure generated by incremental changes in intraluminal volume (delta V/delta P). Postprandial blood levels of these hormones did not affect ileal perfusion pressure. However, higher blood levels of secretin and GIP did significantly lower perfusion pressure. Wall compliance was significantly increased by postprandial blood levels of secretin and GIP, while postprandial blood levels of CCK-8 decreased compliance. Gastrin was without effect on compliance. These data suggest these hormones do not contribute to postprandial ileal hyperemia. However, secretin, GIP, and CCK-8 do affect the postprandial activity of ileal visceral smooth muscle.