Aromatization of 19-norandrogens by porcine leydig cells

The aromatization of norandrogens was investigated with highly purified preparations of Leydig cells from mature male pigs. Cell incubations with norandrostenedione and nortestosterone gave rise to large amounts of estrone sulfate in the medium as determined directly by a specific radioimmunoassay (RIA). Estrogen production was at least equal to that seen with androstenedione and testosterone as substrates. Similar findings were made with cells in culture for 5 days before addition of the androgen substrates in a 4 h-test of aromatase activity. Stimulation of estrogen formation was noted when cells were exposed for 48 h to either hCG (0.5 i.u.) or FGF-β (10 ng) daily, as a pretreatment, before adding androstenedione for the test of aromatase activity. Little or no increase was seen with norandrostenedione or nortestosterone as substrate. Further evidence for estrogen production was obtained from HPLC separations of metabolites of cell incubations with norandrostenedione and [ 14C]nortestosterone monitored by RIA and radioactivity, respectively. It is suggested that norandrogens could serve as important substrates for aromatization in the boar testes.