title: Relaxing effects of phytoestrogen alpha-zearalanol on rat thoracic aorta rings in vitro.
abstract: The aim of this research is to investigate the vasorelaxing effects and mechanisms involved in the phytoestrogen alpha-zearalanol (alpha-ZAL) in rat thoracic aortas rings. Intact or endothelium denuded rat thoracic aortas rings were put in individual organ chamber to observe the endothelium-dependent or independent vasorelaxing effects of alpha-ZAL (10(-10)-10(-5) M). The thoracic aortas rings were pre-contracted with phenylephrine. The relaxing effects of alpha-ZAL were observed and the influence of N(omega)-nitro-L-arginine methylester (L-NAME, NOS inhibitor), methylene blue (MB, guanylate cyclase inhibitor), charybdotoxin (ChTX, Ca(2+)-activated K+ channel blocker), glibenclamide (ATP-sensitive K+ channel blocker), (-) BayK8644 (L-type Ca2+ channel agonist) and ICI182,780 (estrogen receptor antagonist) were pre-incubated with alpha-ZAL, respectively, to explore the possible mechanisms involved in this vasorelaxation. Furthermore, the Phospho-eNOS expression and cGMP level in the aortas tissue were detected by Western blot and radioimmunity, respectively; the NO level in perfusate was assaied by chromatometry. Our result showed that alpha-ZAL (10(-10)-10(-5) M) induced both endothelium-dependent and -independent relaxation of rat thoracic aortas rings. The vasorelaxing effects of alpha-ZAL were dose-dependent whether the endothelium was intact or not. In endothelium-intact aortas rings, alpha-ZAL-induced vasorelaxation might be inhibited by L-NAME, MB, charybdotoxin, glibenclamide and (-) BayK8644, but not ICI182,780. (-) BayK8644 could also inhibit alpha-ZAL-induced vasorelaxation in endothelium-denuded aortas rings.10(-7)-10(-5) M alpha-ZAL might induce the Phospho-eNOS expression in thoracic aorta tissue, increase the NO level in perfusate and cGMP content in thoracic aorta tissue. Meanwhile, L-NAME might decrease both NO and its downstream cGMP level. Methylene blue might decrease the level of cGMP. These results suggest that alpha-ZAL induces a partly endothelium-dependent relaxation of rat thoracic aortas rings; the possible mechanisms involved in this rapid vasorelaxation include activation of eNOS/NO/cGMP pathway, opening of VSMCs ATP-sensitive and Ca(2+)-activated K+ channels through secretion of EDHF from endothelium. Furthermore, this relaxation also appears to be mediated by both direct and indirect inhibition of voltage-dependent Ca2+ channel of VSMCs, while it is not concerned with activation of estrogen receptor.
authors.affiliation: Department of Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing 100069, People's Republic of China.
authors.forename: Wen
authors.initials: W
authors.lastname: Wang
authors.forename: Dongqiao
authors.initials: D
authors.lastname: Jiang
authors.forename: Yingfen
authors.initials: Y
authors.lastname: Zhu
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Jinhong
authors.initials: J
authors.lastname: Duan
authors.forename: Sunling
authors.initials: S
authors.lastname: Dai
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D018999:Charybdotoxin / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004958:Estradiol / Q000031:analogs & derivatives / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology; D005260:Female; D000077267:Fulvestrant; D066298:In Vitro Techniques; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D048789:Phytoestrogens / Q000494:pharmacology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011960:Receptors, Estrogen / Q000037:antagonists & inhibitors / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects*; D015029:Zeranol / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D004965:Estrogen Antagonists; D048789:Phytoestrogens; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011960:Receptors, Estrogen; C029659:zearalenol; D018999:Charybdotoxin; D000077267:Fulvestrant; D009569:Nitric Oxide; D004958:Estradiol; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D015029:Zeranol; D019001:Nitric Oxide Synthase; D006152:Cyclic GMP; D019331:NG-Nitroarginine Methyl Ester