BINDING OF ADENOSINE TO THE CRUDE PLASMA-MEMBRANE FRACTION ISOLATED FROM DOG CORONARY AND CAROTID ARTERIES

Abstract

To elucidate the mechanism of action of adenosine, specific adenosine binding was determined by using plasma membrane rich microsomal fraction of dog coronary and carotid arteries. The binding of adenosine to both coronary and carotid preparations was temperature and pH dependent and was inhibited by aminophylline and adenosine nucleotides. Scatchard analysis of the saturable binding data on carotid arteries exhibited a single species of binding sites with a Kd value of 1.34 .times. 10-6 M and binding capacity of 140 pmol/mg protein. The 1st order Kd of adenosine binding to carotid preparation was 0.0247/min. The nonlinearity of equilibrium binding data (Scatchard Plot) and dissociation curve of binding to coronary arteries suggested the presence of > 1 population of binding sites. The binding sites located in the microsomal fraction of coronary and carotid arteries apparently possess the basic characteristics of the receptors which might be involved in the vasodilatory action of adenosine.