Intratesticular site of aromatization in the human.

To determine the intratesticular site of aromatization, homogenates of separated seminiferous tubules and intact tissue from human testes were incubated with [3H] androstenedione or [3H] testosterone. [3H] Estrogens were isolated and identified, and the amounts synthesized were expressed as pmol/mg protein incubated. In testicular tissue from the three adult subjects investigated, the total estrogen per mg protein was 1.5-2.7 times greater in intact tissue than in isolated seminiferous tubules. This suggests that the major site of aromatization in human testes is the interstitial tissue. Estradiol was by far the major estrogenic product. No differences were observed in the amount of estrogens synthesized whether the substrate was androstenedione or testosterone.