title: Ligand selectivity of dog coronary adenosine receptor resembles that of adenylate cyclase stimulatory (Ra) receptors.
abstract: Adenosine receptors on the surface of coronary myocytes initiate coronary relaxation, but events subsequent to receptor occupancy are uncertain. We assayed the coronary vasoactivity of receptor-selective adenosine analogs in open chest dogs to test the hypothesis that the coronary adenosine receptor is an adenylate cyclase stimulatory (Ra) receptor. The potency order was: ethyl adenosine-5'-uronamide greater than cyclopropyl adenosine-5'-uronamide greater than 2-chloroadenosine greater than N6-[R(-)-1-phenyl-2-propyl] adenosine (R-PIA) greater than N6-cyclohexyladenosine greater than adenosine greater than S-PIA. Such a hierarchy of activity resembles that of the Ra receptors of thyroid and aortic myocyte adenylate cyclases and of tracheal smooth muscle relaxation. The potency order R-PIA greater than adenosine and the stereoselective coronary vasoactivity of R-PIA suggest that the coronary receptor may be a hybrid receptor which contains the "N6 site" typical of inhibitory (Ri) receptors in addition to the "5'-uronamide site' which expresses Ra activity.
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives / Q000502:physiology*; D000262:Adenylyl Cyclases / Q000502:physiology*; D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D004285:Dogs; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000502:physiology*; D011983:Receptors, Purinergic; D014666:Vasomotor System / Q000187:drug effects / Q000502:physiology*
chemical_list: D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; D000262:Adenylyl Cyclases; D000241:Adenosine