Effects of some organophosphorus compounds on the binding of a radioligand (8‐cyclopentyl 1, 3‐[ 3 H]dipropylxanthine) to adenosine receptors in ovine cardiac membranes

8‐Cyclopentyl‐1,3‐[ 3 H] dipropylxanthine ([ 3 H]CPX) is a potent radioligand that specifically binds to the A 1 adenosine receptors. Its high specificity makes it a suitable ligand for the characterization of A 1 adenosine receptors in tissues with low receptor densities. We have demonstrated that the organophosphorus compounds soman, tabun and sarin, at relatively high concentrations, all bind to the A 1 adenosine receptors in ovine cardiac membranes with K i values of 36.7, 328 and 175 μM, respectively. The binding of soman to the receptor site was found to be totally reversible. We suggested that these organophosphorus compounds affect the mechanical responses of the heart through interaction with a potassium channel that does not seem to be closely linked to the A 1 adenosine receptors.