EVIDENCE FOR SEPARATE PGD2 AND PGF2-ALPHA RECEPTORS IN THE CANINE MESENTERIC VASCULAR BED

Potential interactions between PGD2 and PGF2α in the mesenteric and renal vascular beds were investigated in the anesthetized dog. Regional blood flows were measured with electromagnetic flow probes. PGD2, PGF2α and Norepinephrine (NE) were injected as a bolus directly into the appropriate artery, and responses to these agents were obtained before, during and after infusion of either PGD2 or PGF2α into the left ventricle. In each case, the infused prostaglandin caused vascular effects of its own. Left ventricular infusion of PGD2 reduced responses to local injections of PGD2 in the intestine, and a similar effect was observed for PGF2α, suggesting significant receptor or receptor-like interactions for each of the prostanoids. However, systemic infusion of prostaglandin F2α (20-100 ng/kg/min) had no effect on renal or mesenteric vascular responses to local injection of prostaglandin D2. Similarly, PGD2 administration (100 ng/kg/min) did not affect responses to PGF2α in the intestine. The present results therefore suggest that these prostaglandins, i.e., D2 and F2α, act through separate receptors in the mesenteric and renal vascular beds. In addition, increased prostaglandin F2α levels produced by infusion of F2α reduced mesenteric but not renal blood flow, suggesting that redistribution of cardiac output might participate in side effects often observed with clinical use of this prostaglandin, such as nausea and abdominal pain. © 1979.