Effects of Short-Term Bilateral and Unilateral Castration and Androgen Replacement on the Metabolism of [3h]testosterone in Vitro by the Epididymis of the Immature Rat

Abstract

The in-vitro metabolism of [3H]testosterone by the epididymis of the pubertal rat (55 days of age) has been examined after short-term bilateral and unilateral castration and androgen replacement. Bilateral castration did not decrease the metabolism of [3H]testosterone, but did result in a decline in the proportion of 5\g=a\-dihydrotestosterone produced and an increase in that of 5\g=a\-androstane-3\g=a\,17\g=b\-diol, androsterone and 5\g=a\-androstane-3,17-dione.Changes in metabolism occurred in the caput within 2 days after surgery, but not until 5 days after surgery in the cauda epididymidis. Daily testosterone treatment, which maintained prostatic growth in bilaterally castrated animals, did not restore normal androgen metabolism and increased further the production of androsterone and 5\g=a\-androstanedione by the cauda. In unilaterally castrated animals, androgen metabolism in epididymal tissue from the operated side was normal in the cauda but was indistinguishable in the caput from that of bilaterally castrated rats. These results indicate that (a) androgen metabolism by the caput, compared to that by the cauda, responds more quickly to androgen withdrawal and (b) that in the short term, normal androgen metabolism by the caput, but not the cauda, is dependent upon the presence of the ipsilateral testis. Furthermore, testosterone alone proved an inadequate replacement for bilateral castration which implies that the pubertal rat testis secretes additional compounds which are essential for normal function of the epididymis.

On the Androgen Microenvironment of Maturing Spermatozoa*

“…Epididymal tissue can convert T synthesized in the testis to DHT (16,17), and epididymal tissue contains the enzyme 5a-reductase which reduces T to DHT. The tissue concentrations and activity of this enzyme are under testicular control (18)(19)(20).…”

Social behaviour and testicular activity of juvenile rats

“…There are similar data in the literature on reproductive physiology which suggest a reduced sensitivity to exogenous testosterone in rats 35-40 days of age (Foreman & Weeks, 1978;Foldsey & Leathern, 1981). A significant hormonal change in gonadally intact male rats is the gradual onset of surging gonadotrophin-releasing hormone (GnRH) and luteinizing hormone (LH) which occurs in rats around day 35 (de Jong & Sharpe, 1977;Bourguignon, Gerard & Franchimont, 1984), before the pubertal surge of testosterone (Goldman, 1981).…”