title: Endothelium-dependent and -independent coronary relaxation induced by urocortin.
abstract: Urocortin, a newly identified polypeptide, possesses cardiac effects. However, the underlying mechanism of its coronary action is still unclear. In the present study we investigated the possible role of endothelial nitric oxide and Ba2+-sensitive K+ channels in the endothelium-dependent relaxant response to urocortin in the isolated rat left anterior descending coronary arteries. Changes of vessel tone were measured in microvessel myographs. Urocortin produced both endothelium-dependent and -independent relaxation with IC50 of 2.52 nM and 16.5 nM, respectively. Denuation of endothelium decreased the relaxing potency of urocortin. In the endothelium-intact rings pretreated with 100 microM N(G)-nitro-L-arginine methyl ester (L-NAME) or 10 microM 1H-[1,2,4]oxadiazolo[4,2-alpha]quinoxalin-1-one (ODQ), the urocortin-induced relaxation was similar to that observed in endothelium-denuded rings. The relaxant response to urocortin was markedly reduced in endothelium-intact rings preconstricted by 35 mM K+. Pretreatment with 100 microM BaCl2 significantly reduced urocortin-induced relaxation without an effect on the maximum relaxation. Combined treatment with BaCl2 plus L-NAME did not produce additive inhibition. In contrast, BaCl2 did not alter urocortin-induced relaxation in the endothelium-denuded rings. In the endothelium-denuded rings, BaCl2 at 100 microM also inhibited nitric oxide donor-induced relaxation. In conclusion, our results suggest that urocortin-induced endothelium-dependent relaxation of rat coronary arteries is primarily mediated by endothelial nitric oxide and subsequent activation of Ba2+-sensitive K+ channels. The urocortin-induced endothelium-dependent relaxation appears to be cyclic GMP-dependent.
authors.affiliation: Department of Physiology, Faculty of Medicine, the Chinese University of Hong Kong, Shatin, NT, Hong Kong, China.
authors.forename: Xiaoqiang
authors.initials: X
authors.lastname: Yao
authors.forename: Guo-Wei
authors.initials: GW
authors.lastname: He
authors.forename: Franky Leung
authors.initials: FL
authors.lastname: Chan
authors.forename: Chi-Wai
authors.initials: CW
authors.lastname: Lau
authors.forename: Suk-Ying
authors.initials: SY
authors.lastname: Tsang
authors.forename: Zhen-Yu
authors.initials: ZY
authors.lastname: Chen
authors.forename: Yu
authors.initials: Y
authors.lastname: Huang
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D017609:Barium Compounds / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects*; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019811:Hydroxylamine / Q000494:pharmacology; D008297:Male; D023421:Models, Animal; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D015221:Potassium Channels / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D054832:Urocortins; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D017609:Barium Compounds; D002712:Chlorides; D004791:Enzyme Inhibitors; D018696:Neuroprotective Agents; D020030:Nitric Oxide Donors; D015221:Potassium Channels; D054832:Urocortins; D014662:Vasoconstrictor Agents; C024986:barium chloride; D009599:Nitroprusside; D019811:Hydroxylamine; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D003346:Corticotropin-Releasing Hormone; D019331:NG-Nitroarginine Methyl Ester