Influence of endothelium on responses of isolated dog coronary artery to beta-adrenoceptor agonists.

ABSTRACT

AIM: 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. CONCLUSION: 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.