Prostaglandin Regulation of Colonic Blood Flow in Rabbit Colitis

Human and experimental colitis are associated with release of both vasoconstrictor and vasodilator eico-sanoids. To determine the pattern of colonic blood flow in vivo and the role of prostaglandins and thromboxanes, immune complex-mediated colitis and delayed hypersensitivity-mediated colitis were induced in rabbits. Organ blood flow was determined in conscious animals by radiolabeled microspheres before and after cyclooxygenase or thromboxane synthetase inhibition. Colonic blood flow was twofold higher in colitis than in control animals. Thromboxane synthetase inhibition with dazoxiben caused a slight further increase of colon perfusion in animals with colitis, but thromboxane receptor blockade had no effect. Prostaglandin inhibition with indomethacin and ibuprofen did not affect blood flow in controls, but in animals with colitis these drugs markedly reduced colonic blood flow to the level of control animals. The data demonstrate that vasodilatory prostaglandins enhance colonic blood flow in acute colon inflammation.