title: Characterization of [3H]-adenosine binding to media membranes of hog carotid arteries.
abstract: Binding of [3H]-adenosine to a microsomal fraction derived from media strips of hog carotid arteries was studied by a centrifugation technique. Specific binding was very rapid, readily and completely reversible, and temperature dependent. Under the chosen conditions of incubation, at 4 degrees C and in the presence of deoxycoformycin, about 95% of the bound radioactivity was chromatographically identified as adenosine. Scatchard analysis revealed a small number (1.7 pmol/mg protein) of high affinity (KD = 0.23 mumol/l) and a large number (21.6 pmol/mg protein) of low affinity binding sites (KD = 4.3 mumol/l). 5'-Phosphorylated adenosine compounds. 5'-deoxyadenosine, 2-chloroadenosine, and adenosine-5'-N-ethylcarboxamide, all derivatives of adenosine with pronounced vasodilatory properties, were most potent in displacing [3H]-adenosine from its binding sites with IC50 values ranging from 1.8 to 14.3 mumol/l. However, 2-chloroadenosine and (--)N6-phenylisopropyladenosine were weaker competitors of binding than adenosine, which disagrees with the pharmacological findings. Moreover, the IC50 of aminophylline was much higher than the concentration required for half-maximal inhibition of the biological actions of adenosine. This partial lack of specificity may be due to nonreceptor binding of [3H]-adenosine at the low affinity sites.
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002339:Carotid Arteries / Q000378:metabolism*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism*; D013552:Swine; D014316:Tritium
chemical_list: D014316:Tritium; D000241:Adenosine