Effect of testosterone, its 5 alpha-reduced metabolites and the corresponding propionates on testosterone metabolism--II. In the ventral prostate and in the seminal vesicles

Factors influencing prostatic 5 alpha-reductase activity in possum (Trichosurus vulpecula)

1. There were marked differences in prostatic wts among individual possums, but no evidence of a seasonally related change in wt could be established. It was concluded that the wt differences are mainly due to the changes in secretory activities. After castration the prostate wts fell while after administration of testosterone or oestradiol partially reversed this process. 2. Seven steroid conversion products were isolated from prostatic homogenates incubated with [3H] testosterone; 5 alpha-androstane-3 beta,17 beta-diol forming the highest yield. 3. While the 5 alpha-reductase activity of prostates from intact possums was very low (approx. 8% of the total yield), it increased to over 50% after castration. 4. Administration of testosterone or oestradiol partially reversed the post-castration rise in 5 alpha-reductase, while 17 beta-hydroxy-5 alpha-androstane-3-one (DHT) was ineffective. Administration of porcine FSH-NIH-P2 to both intact or castrated possums caused a marked rise in prostatic 5 alpha-reductase activity. 5. It was concluded that in possum, FSH may have a direct stimulatory effect on prostatic 5 alpha-reductase activity. The results are discussed in relation to placental mammals.

Testosterone 5 alpha-reductase in discrete hypothalamic nuclear areas in the rat: effect of castration

The conversion of testosterone into 5 alpha-dihydrotestosterone (DHT) has been studied in different hypothalamic nuclear areas and in the superficial layers of the cerebral cortex of normal and castrated male rats. The tissue fragments utilized in each incubation have been punched from frozen brain sections utilizing calibrated needles. Castration has been performed 12 (short term) and 180 (long term) days before sacrifice. The nuclear areas studied include: the medial preoptic nucleus (MPN), the lateral preoptic nucleus (LPN), the anterior hypothalamic nucleus (AHN), the lateral hypothalamic nucleus (LHN), the posterior hypothalamic nucleus (PHN), the nucleus ventromedialis (HVM), the arcuate nucleus (AR), the median eminence (ME), the nucleus paraventricularis (HPV), the supraoptic nucleus (SO) and the suprachiasmatic nucleus (SC). The possible effect of castration on the 5 alpha-reductase, were assessed in the MPN,LPN,AHN,LHN,PHN and in the cerebral cortex. The results indicate that, in the male rat: 1) the lateral preoptic(LPN) and the lateral hypothalamic nuclei(LHN) possess a 5 alpha-reductase activity higher than that present in the cerebral cortex and in the other hypothalamic nuclei considered; 2)the suprachiasmatic nucleus (SC) apparently possesses a testosterone metabolizing activity lower than that found in any other nervous structures studied so far; 3) castration does not seem to influence the 5 alpha-reductase activity either in the hypothalamic nuclear structures considered or in the cerebral cortex.

Administration of constant low doses of androgens to steers by silastic implant. Suppression of gonadotropins and peripheral conversion of androgens

Yearling Hereford calves approximately 300 kg in weight were castrated and assigned to one of six treatment groups receiving subcutaneous implants (3 implants, 0.5 cm diameter by 10 cm length, 10% steroid by weight) of either androstenedione (D); testosterone (T); 5 alpha-androstane-3 beta, 17 beta-diol (3 beta-diol); dihydrotestosterone (DHT); androsterone (A); or control (no steroid). Blood samples were obtained at half-hour intervals for eight hours one day prior to, and one week after, castration. The castration-induced elevation in FSH secretion was suppressed or modified by the DHT, T, and 3 beta-diol implants. LH levels were not significantly suppressed. The T implants elevated serum T concentrations; DHT implants elevated serum 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) and 3 beta-diol, but not DHT concentrations; 3 beta-diol implants elevated serum 3 beta-diol concentrations. The effects of D and A implants upon serum androgen concentrations were not statistically significant, although observations in vitro suggested an adequate release rate. These data imply that T and DHT, or metabolites of DHT, suppress FSH secretion and suggest that extensive peripheral androgen metabolism occurs.

Quantitation of six androgens by combined high performance liquid chromatography and radioimmunoassay

A technique was developed to separate six androgens (testosterone, dihydrotestosterone, androstenedione, 5 alpha-androstane-3 alpha, 17 beta-diol, 5 alpha-androstane-3 beta, 17 beta-diol, and androsterone) by high performance liquid chromatography prior to quantitation by specific radioimmunoassay systems. Methanol:water (60:40 v:v) was used as the solvent system with a C18 reversed-phase column. The method was verified and used to quantitate the androgens in serum from adult rams bled every 20 minutes for 6 hours and yearling bulls bled every 30 minutes for 8 hours. Concentrations of all 6 androgens varied in an episodic manner with testosterone being the dominant androgen.