Metabolism in vitro of dihydrotestosterone, 5α-androstane 3α, 17β-diol and its 3β-epimer, three metabolites of testosterone, by three of its target tissues, the anterior pituitary, the medial basal hypothalamus and the seminiferous tubules

To examine the metabolism of three 5α-reduced derivatives of testosterone (T) by seminiferous tubules (ST), anterior pituitary (AP) and medial basal hypothalamus (MBH) of adult rats, these tissues were incubated with either tritiated dihydrotestosterone (DHT), α-androstan-3α, 17β diol (3α-adiol) or its 3β-epimer (3β-adiol). The products and residual precursors were quantified using ¹⁴C labeled tracers for recovery. Both DHT and 3β-adiol were extensively metabolized. The % DHT metabolized ranged from 60% (MBH) to 93% (ST) with 3α-adiol forming the major product (ST = 69%, AP = 54%, MBH = 38%). The % 3β-adiol metabolized ranged from 68% (ST) to 90% (AP). The metabolism of 3β-adiol by ST differed from that by the other tissues; reversibility of 3β-oxidoreduction, with substantial accumulation of DHT (13%) and 3α-adiol (36%) occurred only with ST. With AP and MBH these metabolites were identifiable only with increased substrate concentrations. In all incubations with AP and MBH with 3β-adiol the bulk of the radioactivity was associated with some polar metabolites (AP = 76%, MBH = 62%). An inverse relationship between polar metabolite formation and 3/gb-oxidation was suggested by the much smaller amounts of such metabolites being formed by ST. In all tissues the bulk of 3α-adiol remained unmetabolized. The % conversion of 3a-adiol to DHT was relatively high for AP and MBH (av = 27%) but low for ST (av = 7%).