title: Relaxation by adenosine and its analogs of potassium-contracted human coronary arteries.
abstract: The present study was an attempt to characterize the adenosine receptor in human coronary arteries, and to establish the dependence of the relaxations mediated by this receptor on a functional endothelium. Human coronary arteries were obtained from organ donors. Adenosine and its analogs (5'-N-ethyl-carboxamido-adenosine, NECA; N6-L-phenylisopropyladenosine, L-PIA; 2-chloroadenosine, CAD), all inhibited the contraction induced by 25 mmol/l KCl in a concentration-dependent manner and the order of potency was found to be: NECA greater than CAD greater than L-PIA greater than adenosine. These relaxations were antagonized by 8-phenyltheophylline (8PT). At higher concentrations of KCl, the relaxations were attenuated. In rings which relaxed in response to endothelium-dependent relaxing agents (bradykinin and A23187), NECA and CAD produced relaxations similar to those produced in rings which did not show endothelium-dependent responses. The results suggest that the coronary adenosine receptor (probably A2) mediates relaxations which may not be dependent on the relaxing function of the endothelium.
authors.affiliation: Department of Pharmacology, School of Medicine, East Carolina University, Greenville, NC 27858-4354.
authors.forename: M H
authors.initials: MH
authors.lastname: Sabouni
authors.forename: M V
authors.initials: MV
authors.lastname: Ramagopal
authors.forename: S J
authors.initials: SJ
authors.lastname: Mustafa
mesh_terms: D015762:2-Chloroadenosine / Q000494:pharmacology; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D019830:Adenosine-5'-(N-ethylcarboxamide); D000328:Adult; D003331:Coronary Vessels / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010660:Phenylisopropyladenosine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D011983:Receptors, Purinergic / Q000187:drug effects
chemical_list: D011983:Receptors, Purinergic; D015762:2-Chloroadenosine; D010660:Phenylisopropyladenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); D000241:Adenosine; D011188:Potassium