Relation between intestinal blood flow and oxygen uptake

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Abstract
In autoperfused and pump-perfused preparations of canine ileum, arterial pressure, venous outflow pressure, blood flow and arteriovenous O2 difference were measured while blood flow was altered either mechanically or by graded intra-arterial infusions of isoproterenol, adenosine or 2,4-dinitrophenol. In pump-perfused preparations, mechanical alterations in blood flow resulted in opposite changes in arteriovenous O2 difference, so that ileal O2 uptake was independent of blood flow over the range of 30-140 ml.cntdot.min-1.cntdot.100 g-1. Only at flow rates < 30 ml.cntdot.min-1.cntdot.100 g-1 was O2 uptake dependent on blood flow. Isoproterenol, adenosine and dinitrophenol produced dose-dependent increases in blood flow under free-flow conditions and decreases in perfusion pressure under constant-flow conditions. Ileal O2 uptake was not affected by isoproterenol, decreased by adenosine and increased by dinitrophenol. The effects of these drugs on intestinal O2 uptake are in accord with their effects on O2 consumption in vitro. Apparently, vasodilators will not alter intestinal O2 uptake in autoperfused preparations in which O2 uptake is independent of blood flow, unless they exert an effect on oxidative metabolism.

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