Regulation of cyclic guanosine 3',5'-monophosphate in interstitial cells of the rat testis.

: The present studies were performed to evaluate the role of luteinizing hormone (LH) and calcium on cyclic guanosine 3',5'-monophosphate (cyclic GMP) formation in rat testicular interstitial cells. Dose related increases were observed in both intra-and extra-cellular cyclic GMP when various concentrations of LH (1, 10, 100 mlU/ml) were added to the purified Leydig cells. Cyclic GMP was also increased significantly with calcium ionophore A23187 at concentrations of 0.1, 1 and 10 microgram/ml. Adding LH concomitantly with A23187 resulted in a synergistic response and greatly enhanced cyclic GMP formation. When interstitial cells were incubated in calcium-free medium with 1 mM EGTA, the effects of LH and 123187 on cyclic GMP formation were abolished. These data suggest that LH and A23187 can increase cyclic GMP formation in interstitial cells and this response requires extracellular calcium.