Involvement of endogenously produced nitric oxide in the mechanism of histamine-induced inhibition of Leydig cell steroidogenesis via HRH1 receptor subtypes

MONDILLO, CAROLINA; PAGOTTO ROMINA MARÍA; RECHE, CECILIA; PATRIGNANI, ZORAIDA; CYMERYNG, CORA; PIGNATARO, OMAR PEDRO

Hawaii-USA

Congreso; 41st Annual Meeting of The Society For The Study of Reproduction (SSR); 2008

Society for the Study of Reproduction

Abstract The present study was conducted to shed light on the so far unexplored intracellular mechanisms underlying negative modulation of Leydig cell steroidogenesis by histamine (HA). Using the MA-10 cell line and highly purified rat Leydig cells as experimental models, we examined the effect of  the amine on biochemical steps known to be modulated by HA, or involved in LH/hCG action. In agreement with previous findings, HA at 10 ìM showed a potent inhibitory effect on hCG-stimulated steroid production, regardless of the gonadotropin concentration used. HA was almost equally effective at inhibiting db-cAMP-stimulated steroid synthesis. The antisteroidogenic action of HA was blocked by addition of the PLC-inhibitor U73122, and HA significantly augmented IP3 production, suggesting a major role for the PLC/IP3 pathway in HA-induced inhibition of Leydig cell function. Moreover, HA increased nitric oxide synthase (NOS) activity, and the NOS inhibitor L-NG-nitro-arginine methyl ester (L-NAME) markedly attenuated the effect of the amine on steroid synthesis. Considering the site(s) of action of HA, our results show the amine would inhibit steroidogenic acute regulatory (StAR) protein expression, as well as enzymatic steps catalyzed by P450-dependent enzymes of the steroidgenic pathway, mainly the conversion of cholesterol to pregnenolone by cholesterol side-chain cleavage enzyme (CYP11A). Finally, HA also induced a significant decrease in LH/hCG-stimulated cAMP production. On the basis of our findings, HA would antagonize the gonadotropin action in Leydig cells at steps both pre- and post-cAMP formation. Endogenously generated NO would play a role as intracellular mediator of HA antisteroidogenic actions.