PGE1 and hCG Responsive Adenylyl Cyclases in Interstitial Cells from Rat Testis: Biphasic Effects of Calcium

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Abstract
The effects of PGE1 (10 μg/ml), hCG (10 mIU/ml) and Ca2+ (0–10 mM) on rat interstitial cell adenylyl cyclase (AC) activity have been investigated. Like hCG, PGE1 also stimulated membrane bound AC, and both hormonal effects proved to be influenced by Ca2+. Low concentrations of Ca2+ (0.3 mM) enhanced hormonal stimulation, while high concentrations (up to 10 mM) suppressed AC activity. Relative stimulations caused by PGE1 and hCG were maximal in the presence of 0.6 mM Ca2+. Ovine FSH (NIH‐S12), at concentrations causing maximal activation of AC in seminiferous tubules (12.5 μg/ml), had no effect on AC in interstitial cells. Germinal cell membranes displayed insignificant AC activity. We therefore conclude that the AC activity stimulable by PGE1 is located on Leydig cell membranes and that both PGE1 and hCG activities are susceptible to regulation by Ca2+.