Stimulation by cAMP of erythropoietin secretion by an established human renal carcinoma cell line

We used our recently reported stable, transformed human renal carcinoma cell line as a model system to study the role of 3',5'-adenosine monophosphate (cAMP) in erythropoietin secretion. The erythropoietin produced by these cells is both biologically active and immunologically cross-reactive with purified native human hormone in our radioimmunoassay. Erythropoietin release by these renal carcinoma cells appears to be stimulated by cAMP as well as by the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (MIX). The response to cAMP involves a rapid and enhanced release of hormone, which occurred within 30 minutes of exposure of the cells to the effector and continued for at least 4 hours. Intracellular erythropoietin was higher in the control cultures than in the cells treated with cAMP, suggesting that cAMP stimulates the release of a storage pool of hormone. The ability of cAMP and MIX to elicit the release of erythropoietin suggests that a cAMP-mediated mechanism is involved in the release of this hormone.