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ROLE OF HISTAMINE IN THE INTESTINAL FLOW RESPONSE FOLLOWING MESENTERIC ISCHEMIA

Sudden reperfusion of the gut following prolonged ischemia can itself have more deleterious consequences than the ischemia alone. Studies of vasodilator factors influencing the increased flow on reperfusion are therefore of importance. In the present study, a possible role of histamine in the postischemic flow response was examined after a period of total segmental ischemia. The artery supplying the terminal ileum was occluded in anesthetized dogs. Ischemia of 30 min duration was followed by a 30 min reperfusion period (control postischemic flow response), and the arterial blood flow to the segment was measured. After the control postischemic flow response, one of the following drugs was administered intravenously: histamine H1-or H2-blockers (tripelennamine, .5 mg/kg, cimetidine, 10 mg/kg, ranitidine, 2 mg/kg), cromolyn (a mast cell stabilizer, 25 mg/kg), and aminoguanidine (a diamine oxidase blocker, 50 mg/kg). The 30 min ischemia—30 min reperfusion cycle was then repeated (test postischemic flow response). A 30 min mesenteric ischemia-reperfusion period is reproducible once without a significant change in its hemodynamic parameters. The duration and volume of the postischemic flow response were significantly decreased by cimetidine, ranitidine, or cromolyn, and were increased by aminoguanidine. Tripelennamine did not affect the postischemic vasodilator response. At the onset of reperfusion, a release of endogenous histamine occurs from the gut, originating mainly from mast cells. It is proposed that histamine participates in the postischemic flow response through the H2-receptors.