title: Peptidoleukotrienes induce an endothelium-dependent relaxation of guinea pig main pulmonary artery and thoracic aorta.
abstract: The purpose of our investigation was to assess the role of the endothelium in the vasomotor effects of leukotrienes. Norepinephrine-preconstricted rings isolated from guinea pig main pulmonary artery and thoracic aorta responded to LTC4 and LTD4 with a concentration-dependent relaxation. In endothelium-denuded rings, both LTC4 and LTD4 caused a concentration-dependent contraction. The LTD4 receptor antagonist ICI 198,615 inhibited both LTC4- and LTD4-induced relaxation and contraction. Inhibition of gamma-glutamyl transpeptidase with AT-125 prevented the effects of LTC4, but not those of LTD4. The relaxant effect of LTD4 was not modified by indomethacin, but was abolished by methylene blue. We conclude that: 1) LTD4 induces a receptor-mediated endothelium-dependent relaxation of cavian pulmonary artery and aorta; 2) the vasorelaxant effect of LTC4 requires its conversion to LTD4; 3) the vasorelaxant effect of LTD4 is unrelated to PGI2 release, and is probably due to the release of an "EDRF"; 4) the removal of the endothelium reveals a direct receptor-mediated vasoconstricting effect of leukotrienes.
mesh_terms: D000818:Animals; D001011:Aorta / Q000502:physiology; D001688:Biological Products / Q000502:physiology; D004730:Endothelium, Vascular / Q000502:physiology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009569:Nitric Oxide; D011651:Pulmonary Artery / Q000502:physiology; D013189:SRS-A / Q000494:pharmacology*; D014666:Vasomotor System / Q000187:drug effects*
chemical_list: D001688:Biological Products; D013189:SRS-A; D009569:Nitric Oxide; D007213:Indomethacin