Postprandial intestinal hyperemia: role of bile salts in the ileum.

In an autoperfused dog ileum preparation, artificial pressure, venous outflow pressure, blood flow, and arteriovenous oxygen difference were measured while bile and bile salt solutions, at physiological concentrations, were placed in the lumen. Intraluminal placement of endogenous bile, synthetic bile, or bile salt solutions increased ileal blood flow (99 +/- 10, 94 +/- 20, and 104 +/- 17%, respectively) and oxygen uptake (30 +/- 5, 36 +/- 9, and 28 +/- 5%, respectively). Endogenous bile pretreated with cholestyramine, a bile salt-sequestering resin, did not alter ileal blood flow, yet increased ileal oxygen uptake by 11 +/- 3%, a response similar to that observed while Tyrode's solution (the vehicle) was in the lumen. Intra-arterial infusion of bile salts increased ileal blood flow in a dose-dependent manner, while not significantly altering ileal oxygen uptake. The results of the present study indicate that bile salts play an important role in the functional (postprandial) hyperemia in the ileum by 1) directly dilating the ileal vasculature and 2) enhancing ileal metabolism during their active absorption.