Differential effects of gastrointestinal hormones on the blood flow of the alimentary tract of the dog.

The blood flow of the alimentary tract in anesthetized dogs was measured with radioactively labeled 15-micron microspheres before and after i.v. application of the gastrointestinal hormones glucagon, vasoactive intestinal polypeptide (VIP), secretin, and somatostatin. After 5 min glucagon in a dose of 75 micrograms/kg bolus + 5 micrograms/kg X min-1 infusion increased significantly the blood flow in liver, stomach, duodenum, jejunum, ileum, and colon as well as the cardiac output by 160%, 761%, 662%, 576%, 817.3%, 320%, and 108%, respectively. A dose of 3 ng/kg X min-1 resulted in reduction of the circulation in liver, gastric fundus, duodenum, and colon by 27.7%, 19.1%, 16.2%, and 10.7% after 5 min while the cardiac output was not affected. Vasoactive intestinal polypeptide (VIP) infused in a dose of 3.3 pmol/kg X min-1 for 5 min increased the blood flow in the pancreas by 30% and reduced it in the spleen and gastric corpus by 26.9% and 41.5%, respectively. Secretin, another member of the glucagon family, after a 5-min infusion of a dose of 0.5 CU/kg X min-1 increased the cardiac output by 49.96% and the renal circulation by 120.7%. In the gastrointestinal tract circulation of the gastric antrum was stimulated by 474%, of the duodenum by 93.5% and of the ileal mucosa by 178%. Infusion of the pancreatic hormone somatostatin (3.5 micrograms/kg bolus followed by infusion of 3.5 micrograms/kg X h-1) increased the blood flow in the liver by 13%, in the pancreas by 23.15%, and in the spleen by 29.8%, while it reduced it in the fundic mucosa by 17.1% and corpus mucosa by 28.8%. In summary, the gastrointestinal hormones examined exert marked and distinct effects on the circulation of the gastrointestinal tract, each hormone in different parts of the digestive tract. Thus, the local microcirculation of the gastrointestinal tract seems to be subject to hormonal in addition to nerval control.