THE AFFINITY OF ADENOSINE FOR THE HIGH-AFFINITY AND LOW-AFFINITY STATES OF THE HUMAN ADENOSINE-A(1) RECEPTOR

The affinity of adenosine for the human adenosine A(1) receptor expres sed on Chinese hamster ovary cell membranes has been measured in the p resence and absence of GTP. The competitive effect of endogenous adeno sine on the binding properties of adenosine A, receptors was estimated from differences in the binding of N-6-cyclohexyladenosine measured i n the absence and presence of adenosine deaminase. From these data, th e affinity of adenosine for the high and low-affinity states of the hu man adenosine A(1) receptor (7 X 10(7) and 1.3 X 10(5) M(-1), respecti vely) was calculated.