PT - JOURNAL ARTICLE AU - W H Folger AU - D Lawson AU - C S Wilcox AU - J L Mehta TI - Response of rat thoracic aortic rings to thromboxane mimetic U-46,619: roles of endothelium-derived relaxing factor and thromboxane A2 release. DP - 1991 Aug 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 669--675 VI - 258 IP - 2 4099 - http://jpet.aspetjournals.org/content/258/2/669.short 4100 - http://jpet.aspetjournals.org/content/258/2/669.full SO - J Pharmacol Exp Ther1991 Aug 01; 258 AB - Studies were designed to test the role of the endothelium and endogenous release of thromboxane (Tx) A2 in the contractile response of rat thoracic aortic rings to the TxA2/prostaglandin (PG) H2 mimetic, U-46,619. U-46,619 caused a dose-dependent contraction of rings with endothelium (mean ED50 = 6.54 +/- 3.02 x 10(-9) M; n = 13) which was abolished by the TxA2/PGH2 receptor antagonist, SQ-29,548. Removal of endothelium greatly potentiated (P less than .05) the contractile response to U-46,619 (ED50 = 4.78 +/- 2.14 x 10(-10) M; n = 14). On addition to the organ bath, oxyhemoglobin (10(-6) M), an inhibitor of endothelium-derived relaxing factor, increased vascular smooth muscle contraction in response to U-46,619 and abolished the difference in response between rings with endothelium (ED50 = 6.63 +/- 0.38 x 10(-11) M) and those without (ED50 = 5.13 +/- 0.18 x 10(-11) M). Vascular contraction with U-46,619 (10(-7] was associated with release of immunoreactive TxB2 and 6-keto PGF1 alpha as well as increased conversion of [14C]arachidonate to [14C]TxB2 and 6-keto-[14C]PGF1 alpha. To test the role of endogenous TxA2 in response to U-46,619, the TxA2 synthetase inhibitor UK-38,485 (10(-6) M) was added directly to the organ bath; this diminished (P less than .05) the contractile responses to U-46,619 of rings with and without endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)