Minna Bryan
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The inhibitory effect of MENT, which does not undergo alpha-reduction, was not altered by finasteride. The role of alpha-reductase in the testosterone feedback inhibition of gonadotropin secretion from the pituitary has not been elucidated. Castration has been reported hair loss to increase the alpha-reductase activity in pituitary glands. There was a significantly greater suppression of serum LH in rats receiving T plus finasteride compared with those receiving T alone. A theoretical model was blooming to aid in understanding the in vivo hair loss efficacy data of finasteride. Therefore, we investigated the role of alpha-reductase on T action in in vitro and in vivo models. Subsequent application of the theory to evaluate the propecia in vivo efficacy data of finasteride indicates low effective concentration of finasteride at the inhibition sites permanent hair removal and suggests replenish inhibition of 5AR 2, but insufficient suppression of 5AR finasteride generic 1 at the clinical doses. In an in vivo study, rats castrated for 2 weeks received T with or without finasteride. In the presence of finasteride (a alpha-reductase inhibitor), the inhibition of LH released by T and 19-NT were significantly greater. These results suggested that alpha-reductase in the pituitary is online propecia not obligatory for the inhibitory action of T on gonadotropin secretion in the castrated rat. Hence, the effect of castration duration on the conversion of T to DHT by pituitary homogenates and the responsiveness of pituitary monolayer cell cultures to gonadotropin-releasing hormone (GnRH) challenge exposure were investigated. propecia Hence we used rats castrated for 2 weeks to elucidate the role of alpha-reductase in T feedback inhibition. As shown, this ratio should be in excess of 3 for > 95% inhibition of the target in vivo. does propecia work The inhibitory effects of the androgens T, 19-nortestosterone (19-NT), and 7alpha-methyl-19-nortestosterone (MENT) at 3 different concentrations (10(-9), 10(-7), and 10(-5) mol/L) on GnRH-stimulated LH release from monolayer cell cultures of pituitaries from rats castrated for 2 weeks were examined. MENT sho the ultra inhibition, follo by 19-NT and T. In addition, the GnRH-stimulated release of LH from monolayer cell cultures of pituitaries from rats castrated for 1 day was twofold greater, whereas that from rats castrated for 2 weeks was six- to sixth greater compared with basal luteinizing hormone (LH) release. In vivo time-dependent inhibition of human steroid 5 alpha-reductase by finasteride.Finasteride (17 beta-(N-t-butylcarbamoyl)-4-aza-5 alpha-androstan-1-en-3- one), a time-dependent, irreversible inhibitor of human steroid 5 alpha-reductase (5AR), may only reduce dihydrotestosterone levels in humans by approximately 60% at the doses used clinically. The antigonadotropic action of testosterone but not 7alpha-methyl-19-nortestosterone is attenuated through the alpha-reductase pathway in the castrated male rat pituitary gland.The enzyme alpha-reductase plays a significant role in the prostate to amplify the action of testosterone (T) by converting it to a more potent androgen, dihydrotestosterone (DHT). The action of MENT, a nonreducible androgen, on the pituitary is not affected by alpha-reductase.. All 3 androgens sho dose-dependent inhibition of LH release. According to the theory, whether an enzyme can be inhibited in vivo by an irreversible inhibitor is dependent on the value of a ratio of the observed rate of enzyme inhibition over the rate constant for inhibitor elimination. Incubation of [3H]-T with pituitary homogenates sho that the conversion of T to alpha-reduced metabolites was two- to threefold greater in pituitaries from rats who had been castrated for 14 days compared with those castrated for 1 day.
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