title: Effects of catechins on vascular tone in rat thoracic aorta with endothelium.
abstract: The effects of eight catechin derivatives on vascular tone in rat thoracic aorta were examined. Catechin derivatives (10 microM) potentiated the contractile response to phenylephrine in endothelium-intact arteries. The potentiations produced by EGCg and EGC were almost absent in endothelium-denuded arteries and abolished by N(G)-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthesis. The catechin derivatives also inhibited endothelium-dependent relaxation in response to acetylcholine. The order of catechin derivatives ranked in terms of both increasing vascular reactivity and impairing endothelium-dependent relaxation was similar; (-)-gallocatechin (GC) >or= (-)-epigallocatechin (EGC) >or= (-)-gallocatechin gallate (GCg) >or= (-)-epigallocatechin gallate (EGCg) >or= (-)-catechin (C) >or= (-)-epicatechin (EC) >or= (-)-catechin gallate (Cg) >or= (-)-epicatechin gallate (ECg). In addition, EGC inhibited the endothelium-independent relaxation evoked by both sodium nitroprusside and NOC-7, a spontanous NO releaser, but EGCg inhibited only that by NOC-7. These findings indicate that catechin derivatives produce a potentiation of the contractile response and an inhibition of the vasorelaxant response, probably through inactivation of endothelium-derived nitric oxide (NO), and that the hydroxyl on C-5 of the B ring together with the stereoscopic structure between the C-3 group and the B ring of flavanols was of importance in mediating the above effects and that the substitution of a gallate group of C-3 attenuated the effects, probably due to a decreased response to solube guanylate cyclase in vascular smooth muscle cells.
authors.affiliation: Department of Medicine, Faculty of Pharmaceutical Sciences, Hokuriku University, Kanazawa, Japan. f-sanae@hokuriku-u.ac.jp
authors.forename: Fujiko
authors.initials: F
authors.lastname: Sanae
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Miyaichi
authors.forename: Haruhisa
authors.initials: H
authors.lastname: Kizu
authors.forename: Hisao
authors.initials: H
authors.lastname: Hayashi
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000502:physiology; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004730:Endothelium, Vascular; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014666:Vasomotor System / Q000187:drug effects* / Q000502:physiology
chemical_list: D009842:Oligopeptides; D014662:Vasoconstrictor Agents; C087220:BQ 610; D010656:Phenylephrine; D002392:Catechin; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin