The Sex Pheromone Precursor Androsta-5,16-dien-3β-ol Is a Major Early Metabolite inin VitroPregnenolone Metabolism in Human Testicular Homogenates

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Abstract
In an earlier report we described the early time sequence of the in vitro metabolism of [4-14C]pregnenolone ([4-14C]P5) to testosterone in homogenates of human and rat testes and demonstrated the appearance of mainly .DELTA.5 (humans)- and .DELTA.4 (rats)-steroids within minutes after starting the incubation. In this study strong evidence is presented for the substantial synthesis from P5 of the sex pheromone precursor androsta-5,16-dien-3.beta.-ol (ADL) in human, but not rat, testicular homogenates. The 16-unsaturated C19 steroid ADL appeared after 1 min of incubation, and within 5 min reached values (17-23% of total radioactivity added as [4-14C]P5) comparable to those of the major .DELTA.5-steroids 17.alpha.-hydroxypregnenolone and dehydroepiandrosterone. Thus, in humans, as in boars, the sex attractant precursor ADL is a major early testicular metabolite of P5.