Steroidogenesis and testosterone metabolism in cultured principal cells from the ram epididymis

To determine if ram principal cells can synthesize or metabolize testosterone, or metabolize other steroids present in rete testis fluid, principal cells from the initial segment, central caput, and proximal corpus epididymidis were isolated and cultured in a floating collagen matrix with medium containing 20% dialyzed rete testis fluid. In the first experiment, each matrix was washed twice in testosterone‐free medium on day 2.8, transferred into culture medium containing 100 nM of a tritiated steroid and incubated for 4 hours at 34 C. The tritiated steroids were pregnenolone, 5‐androstene‐3β,17β‐diol, progesterone, 4‐androstene‐3,17‐dione, testosterone, and dihydrotestosterone. Since testosterone was not formed from 5‐androstene‐3β,17β‐diol or 4‐androstene‐3,17‐dione, testosterone synthesis by ram principal cells is unlikely. Pregnenolone and 5‐androstene‐3β,17β‐diol were not metabolized and only slight metabolism of dihydrotestosterone occurred. Progesterone, 4‐androstene‐3,17‐dione, and testosterone were metabolized to 5α‐reduced products tentatively identified as 5α‐pregnane‐3,20‐dione and 5α‐pregnan‐3β‐ol‐20‐one and/or 5α‐pregnan‐20α‐ol‐3‐one; 5α‐androstane‐3,17‐dione and 5α‐androstan‐3α‐ol‐17‐one, and dihydrotestosterone, respectively. The second experiment evaluated testosterone metabolism by both cultured principal cells and minced epididymal tissue. On day 1 of culture, during 12 hours the accumulation of dihydrotestosterone in medium from cells of the central caput was 48 × and 1.1 × that in medium from cells of the initial segment and proximal corpus epididymidis. The difference (P > 0.01) persisted on days 3 and 6 of culture, although testosterone metabolism decreased. For 3‐hour incubations of minced tissue, testosterone metabolism by tissue from the central caput was 3.6 ×, 1.3 x, and 0.9 × that of tissues from the initial segment, distal caput, and proximal corpus, respectively. Thus, testosterone metabolism in the initial segment is low compared with more distal regions.