Comparison of androgen synthesis in human fetal testis and adrenal: 3 -hydroxysteroid dehydrogenase-isomerase and 17 -steroid dehydrognase activities.

To assess comparative 3fi-hydroxysteroid dehydrogenase-isomerase and I7fisteroid dehydrogenase activities in human fetal testis and adrenal, equal weights of adrenal and testicular tissue from the same fetuses were incubated with dehydroepiandrosterone or pregnenolone, under identical conditions. Tissues from five fetuses were investigated. The following products were isolated and quanti tated: dehydroepiandrosterone, androstenediol, androstenedione and testosterone. The 3/3-hydroxysteroid dehydrogenase-isomerase activity, expressed as pmoles found in androstenedione plus testosterone per mg protein incubated, was 3.5-138 times higher in testicular than in adrenal tissue. I7~-Steroid dehydrogenase activity expressed as pmoles found in testosterone plus androstenediol per mg protein incubated was 73-313 in testicular tissue compared to o-2.64 in adrenal tissue. When the same activities were expressed in terms of activity per total adrenal and testicular tissue per fetus, the i7fi-steroid dehydrogenase activity was still considerably higher in testes than in adrenals, while the 3fl-hydroxysteroid dehydrogenase-isomerase activity was higher in the testes of the three smaller fetuses investigated. These data provide additional evidence that tile hmnan fetal testis is geared to the formation of testosterone which is essential for genital development in the male fetus.