title: [3H]adenosine binding to bovine coronary arteries and myocardium.
abstract: The characteristics of [3H]adenosine binding to bovine myocardial and coronary tissue were investigated using the microsomal fraction obtained by fractionated centrifugation. Binding experiments consisting of equilibrium, kinetic and competition studies were performed employing a filtration assay. The coronary microsomal fraction yielded two classes of binding sites with different affinities and binding capacities. The approximate binding parameters were: KD = 1.7 x 10(-7) M, Bmax = 1.2 pmol/mg protein, and KD = 2.6 x 10(-6) M, Bmax = 6.6 pmol/mg protein, respectively. Only one single class of binding sites was found in the myocardium as indicated by a linear Scatchard plot (KD = 3.7 x 10(-7) M, Bmax = 11.7 pmol/mg protein). In both tissues competition experiments performed with a number of adenosine analogues displayed similar specificity, i.e. high competing potency of adenosine nucleotides, whereas, 2-chloroadenosine, L-PIA, 2'-deoxyadenosine and theophylline showed little or no affinity. The results presented in this paper do not provide evidence for the predominance of typical Ra sites according to the definition of Londos et al. (Proc. Natl. Acad. Sci. U.S.A. 77, 2551, 1980) in bovine coronary arterial tissue or myocardium.
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D003331:Coronary Vessels / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism; D011983:Receptors, Purinergic; D013806:Theophylline / Q000494:pharmacology
chemical_list: D011956:Receptors, Cell Surface; D011983:Receptors, Purinergic; D013806:Theophylline; D000241:Adenosine