Influence of endothelium on responses of isolated dog coronary artery to beta-adrenoceptor agonists.
OBJECTIVE
To study the role of the endothelium in mediating the response of the coronary arteries to adrenoceptor agonists.


METHODS
Endothelium intact and denuded dog epicardial coronary artery rings were used. The contractile responses were recorded on forcetransducer and a pen recorder.


RESULTS
In all ring segments, norepinephrine (NE) and isoproterenol (Iso) produced concentration-dependent relaxation in the presence and absence of phentolamine. Endothelium-removal decreased this relaxation and depressed the maximal response. Inhibition of nitric oxide synthesis by N omega-nitro-L-arginine-methyl ester induced the same influences as endothelium-removal.


CONCLUSIONS
beta-adrenoceptor agonists produce relaxation of dog coronary artery by both endothelium-dependent and independent mechanisms, endothelium-dependent relaxation induced by beta-adrenoceptor agonists is mediated by nitric oxide.
Tang
Z L
ZL
Department of Pharmacology, Hu-nan Medical University, Changsha, China.
Wu
W J
WJ
Xiong
X M
XM
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects*; D004285:Dogs; D004730:Endothelium, Vascular / Q000502:physiology*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
D000318:Adrenergic beta-Agonists; D007545:Isoproterenol; D009638:Norepinephrine; D010646:Phentolamine