Differential effects of prostaglandins in the mesenteric vascular bed

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Abstract
The effects of prostaglandins (PG) D2, E2, F2.alpha., I2 and arachidonic acid on blood flow in the mesenteric vascular bed were investigated in the anesthetized dog, and the effects of PGD2 and PGF2.alpha. were compared in the kidney and intestine. Blood flow was measured with electromagnetic flow probes. All vasoactive substances were injected intra-arterially, and aortic pressure was unchanged in these experiments. PGD2 and PGF2.alpha. produced dose-related reductions in mesenteric flow, whereas arachidonic acid, PGE2 and PGI2 increased flow in a dose-dependent manner. Mesenteric vasodilator responses to PGI2 and PGE2 were similar and indomethacin decreased the vasodilator response to arachidonic acid by approximately 50%. In contrast to effects in the mesenteric bed, PGD2 increased flow, whereas PGF2.alpha. had little if any effect in the kidney. PGD2 and PGF2.alpha. have differential effects on the intestinal and renal vascular beds and receptors for these PG are different in the 2 regional beds. Arachidonic acid produced vasodilatation in the intestine, and since PGE2 and PGI2 were potent vasodilators, there may be a preferential pathway for the formation of dilator products such as PGI2 and PGE2 in this organ.