Arachidonic acid and postprandial intestinal hyperemia.

The effects of prostaglandin synthesis on food-induced increases in intestinal blood flow and O2 uptake were examined in the jejunum of anesthetized dogs. Intravenous (40 micrograms X kg-1 X min-1) or intra-arterial (0.8-1.6 microgram X min-1) infusions and luminal placement (6.5 X 10(-4) M or 200 micrograms/ml) of arachidonic acid (AA) significantly attenuated the food-induced jejunal hyperemia. Furthermore, luminal placement of AA significantly attenuated the food-induced increase in jejunal O2 uptake. Changes in blood flow and O2 uptake were significantly correlated both before and after arachidonic acid administration. Although intravenous infusion of AA decreased blood flow, intra-arterial infusion and luminal placement of AA did not significantly alter resting blood flow under free-flow conditions. In another series of experiments, intravenous infusions of AA under constant-flow conditions produced a biphasic response: vascular resistance rose when local blood AA concentration was raised to the range between 1 and 6 micrograms/ml blood and fell when the concentration was raised between 8 and 12 micrograms/ml blood. This study indicates that prostaglandin synthesis has a marked effect on both resting intestinal blood flow and postprandial intestinal hyperemia. The attenuation of the hyperemia may be due to its attenuation of the food-induced increase in intestinal oxidative metabolism.