Abstract

CASTILLO, Carlos; CASTILLO, Enrique F.; LOPEZ, Jorge  and  LOPEZ, Ruth M.. Testosterone inhibits the contractile responses to phenilephrine associated with the release of intracellular calcium in rat aorta. Gac. Méd. Méx [online]. 2006, vol.142, n.1, pp.1-8. ISSN 2696-1288.

Using endothelium-denuded rat aortic rings incubated in Ca²⁺-free solution, we assessed the ability of testosterone to influence the contractile effect of phenylephrine, and the increase in resting tone (IRT) associated with Ca²⁺ ability to cross the plasma membrane. The addition of testosterone[10^-5-10^-4M]5 min before phenylephrine [10^-6 M], inhibited both phenylephrine-induced contraction and IRT. These changes were not affected by cycloheximide (10^-5 M; a protein synthesis inhibitor of), flutamide (10^-5 M; an androgenic receptor antagonist), or by adding aminoglutethimide (10^-5 M; an aromatase inhibitor). Testosterone also blocked the contractile response to serotonin [10^-5 M] but not to caffeine [10^-2 M]. On the other hand, testosterone inhibited the contractile responses to cyclopiazonic acid (10^-6 M; a selective Ca²⁺ -ATPase inhibitor) or ryanodine (10^-5 M; an activator of sarcoplasmic reticulum Ca²⁺ -release channels) associated with capacitative Ca²⁺ influx through non-L-type Ca²⁺ channels. These data suggest that by acting on the cellular membrane, testosterone interferes with the signal transduction pathway of G_q-11 protein-coupled receptors, and inhibits capacitative Ca²⁺ influx through both L-type and non-L-type Ca²+ channels. These effects are non-genomic, non-mediated by the intracellular androgen receptor, and not due to the conversion of testosterone to estrogens.

Keywords : Testosterone; intracellular Ca²⁺ release; adrenergic agonists.

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