Desensitization of adenylate cyclase in cultured fibroblasts with prostaglandin E1 and epinephrine.

Pretreatment of intact cultured WI-38 fibroblasts with either prostaglandin E1 (PGEI) or epinephrine progressively desensitized adenylate cyclase. PGEl pretreatment reduced basal, guanyl-5’-yl imidodiphosphate (GPP(NH)P), epinephrineand PGEl-stimulated adenylate cyclase activities with no effect on the fold stimulation of either PGEI or epinephrine. In contrast, epinephrine pretreatment desensitized only the epinephrine-stimulated activity with no effect on basal, GPP(NH)P, or PGEl activities. While the refractory states of adenylate cyclase induced by the two hormones were very different, the time courses of their development and reversal after hormone washout were similar. The tllz for desensitization of adenylate cyclase by either hormone was about 2 to 3 min, and for reversal was approximately 4 to 6 min. These times were in good agreement with those determined from intact cell measurements of adenylate cyclase desensitization and reversal. Also both of the hormone-induced refractory states were very stable, surviving without alteration the procedure for the isolation of the washed membrane fraction. Neither of the refractory states of adenylate cyclase could be reversed by GTP. Our results suggest that there are at least two different mechanisms for the rapid hormone-induced desensitization of adenylate cyclase in WI-38 fibroblasts. The PGEl desensitization appears to be exerted at the level of the adenylate cyclase coupling system since the basal and GPP(NH)P-stimulated adenylate cyclase activities are reduced while the epinephrine effect may be at the level of the P-adrenergic receptor.