Na+ amplifies adenosine receptor-mediated inhibition of adipocyte adenylate cyclase.

Membrane preparations of hamster adipocytes were used to study the inhibition of adenylate cyclase by the adenosine analogue, N6-phenylisopropyladenosine (PIA). Inhibition by PIA was half-maximal and maximal (about 40%) at about 0.03 and 1 micro M, respectively, and was antagonized by 3-isobutyl-1-methylxanthine in a competitive manner. Like other hormone receptor-mediated inhibitions of the adipocyte adenylate cyclase, the adenosine receptor-mediated action on the enzyme was absolutely dependent on GTP and was amplified by sodium ions.