Effects of portacaval anastomosis on glucose tolerance in the dog: evidence of an interaction between the gut and the liver in oral glucose dosposal.

Continuous infusions of glucose (90 min duration) were given into the duodenum (ID), or the portal vein (IP), or a peripheral vein (IV) in conscious dogs, intact dogs, or dogs with portacaval anastomoses. In intact animals ID glucose tolerance was better than IV glucose tolerance, but IP glucose tolerance was not significantly different from IV glucose tolerance. Thus, the superiority of tolerance to ID glucose was not accounted for by relatively high levels of glucose in portal blood. IV glucose tolerance was not significantly affected by protacaval anastomosis with ligation of the portal vein, but ID glucose tolerance was markedly impaired. Disproportionate impairment in tolerance to enterically administered glucose in dogs with portacaval shunts, and the similarity of IP and IV glucose tolerance in intact dogs, suggest that both liver and the gut are important in determination of oral glucose tolerance through mechanisms that have little or no effect on responses to parenterally administered glucose. The results also suggest that the hepatic contribution is not dependent upon portal venous perfusion of the liver, and that a humoral interaction between the gut and the liver is involved which is not simply dependent on endocrine responses of the pancreas.