Testosterone Metabolism by Proximal and Distal Regions of the Vas Deferens from Immature and Mature Rats1

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Abstract
The vas deferens, an androgen-dependent organ, may have physiological importance in sperm maturation, yet very little is known about its steroid capabilities. To explore the steroid metabolic activities and their possible changes during sexual maturation, a comparative study of [14C] testosterone metabolism by the proximal (VDP) and distal (VDD) segments of the vas deferens from immature and mature rats was carried out in vitro. Approximately 50 mg of the VDP and VDD portions of the vas deferens, devoid of spermatozoa, were incubated in duplicates for 3 h at 37.degree. C with [14 C] testosterone (53.5 .mu.Ci/mmol) and the essential cofactors. After the addition of appropriate 3H-labeled recovery tracers to the incubates, the steroids were extracted, separated by paper chromatography and TLC and crystallized to constant 3H/14 C ratio in 3 consecutive crystals. All tissues metabolized [14C] testosterone into 4 major steroids: dihydrotestosterone (DHT), 5a-androstane-3.alpha.-17.beta.-diol (5.alpha.-3.alpha.-diol), .DELTA.4-androstenedione and androsterone. The metabolites accounted for .apprx. 16% and .apprx. 6% of the conversion products in the immature and mature vas deferens respectively. There was no significant difference in [14C]testosterone metabolism when VDP and VDD were compared within either age group of animals. However, the immature vas deferens was significantly more active compared to mature vas deferens in the synthesis of these metabolites, indicating that the activities of 5.alpha.-reductase, 3.alpha.-hydroxysteroid dehydrogenase and 17.beta.-hydroxysteroid dehydrogenase diminish during sexual maturation. The possible physiological significance of these changes during maturation of the vas deferens is discussed.