Effect of anticalmodulin drugs on testosterone synthesis in hCG stimulated mouse Leydig cells
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The effect of three anticalmodulin drugs, prepared in this laboratory and a commercially available drug Mastoparan, was tested on the secretion (or synthesis) of testosterone in hCG stimulated Leydig cells. The results of the use of drugs RN-IV A, RN-IV B and RN-IV C indicated that hCG (10 ng/ml), DbcAMP (0.1 mM) and cholera toxin (2 μg/ml)-stimulated testosterone production was inhibited in Leydig cells in a dose dependent manner. In hCG stimulated cells, the ID50 for drug RN-IV A was 2 μM, for drug RN-IV B was 25 μM and for drug RN-IV C was 130 μM. Based on ID50 the most effective drug was RN-IV A. Maximum inhibition of testosterone production was obtained at a concentration of 20 μM for drug RN-IV A, 150 μM for drug RN-IV B and 200 μM for drug RN-IV C. Further extensive experiments with drug RN-IV B showed that (a) at 100 μM concentration the drug does not impair the binding of receptor with 125I hCG, (b) the cAMP accumulation was prevented in a dose dependent manner reaching a minimal of 1.1 pM at 50 μM, compared with 3.5 pM in hCG (10 ng/ml) stimulated cells. The drug RN-IV B at a concentration of 100 μM, which failed to prevent conversion of exogenous pregnenolone or progesterone to testosterone, otherwise caused complete inhibition of testosterone production in hCG stimulated cells. Mastoparan also inhibited testosterone production in hCG stimulated cells in a dose dependent manner. A much higher dose (75 μM concentration) of Mastoparan was required for complete inhibition of testosterone production than is usually claimed (nanomolar concentration).
En]KeywordsAnticalmodulin drugs hCG DbcAMP cholera toxin Leydig cells
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