Prostaglandins mediate the compensatory responses to hemorrhage in the small intestine of the rat.

We examined the effect of fixed-volume hemorrhage (10 ml/kg) on microvascular diameters and blood flow in the small intestine of the rat using in vivo videomicroscopic techniques. We found that hemorrhage in the absence of a potent cyclooxygenase inhibitor results in a transient decrease in intestinal blood flow and a preferential redistribution of intramural blood flow toward the mucosa because of a localized vasodilator response of the premucosal microvessels. In the presence of the selective cyclooxygenase inhibitor, mefenamic acid, the decrease in intestinal blood flow was more substantial and prolonged, and the localized vasodilator response of the premucosal microvasculature was abolished. Our results suggest that vasodilator prostaglandins contribute to the compensatory response of the intestine to hemorrhage and are responsible for the shunting of blood toward the mucosa during hemorrhagic hypotension.