Prostaglandin E2Causes Contraction of Rat Aortic Rings by Activating Thromboxane A2/endoperoxide Receptors

Abstract

Prostaglandin (PG) I2 causes vasoconstriction in isolated blood vessels and yet lowers blood pressure. This study was conducted to study the vascular effects of PGE2 on isolated vascular tissues. PGE2 (10–2000 ng/ml) caused a concentration-dependent contraction of quiescent rat aortic rings, and the contraction was greater in endothelium-denuded than in endothelium-intact rings. PGE2-induced contraction was also enhanced by prior treatment of quiescent endothelium-intact rat aortic rings with the nitric oxide synthase inhibitor NG -nitro-L-arginine methyl ester (L-NAME), or the nitric oxide inactivator oxyhemoglobin. PGE2 also caused an additional contraction of norepinephrine (NE)-precontracted rat aortic rings, but the additional contraction was similar in endothelium-intact or de-endothelialized rings. Pretreatment of endothelium-intact NE precontracted rings with L-NAME, or oxyhemoglobin, or the endothelin A and B receptors antagonist PD-142,893, or the cyclooxygenase inhibitor indomethacin did not af...