Immunoexpression of the steroidogenic enzymes 3-beta hydroxysteroid dehydrogenase and 17α-hydroxylase, C17,20 lyase and the receptor for luteinizing hormone (LH) in the fetal rat testis suggests that the onset of Leydig cell steroid production is independent of LH action

The production of testosterone in the adult testis is mainly regulated by LH. Testosterone is essential for normal development of the male fetus, The regulation of testosterone production in the fetal testis is less clear than in the adult testis, and there are indications that at Beast the onset of androgen production in the fetal testis takes place in an LH-independent way. The aim of the present study tvas to compare the onset of synthesis and pattern of expression of EW receptors and two important steroidogenic enzymes, 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and 17 alpha-hydroxylase/17,20-lyase (P450(c17)), in fetal rat gonads, Whole fetuses (13.5 and 14.0 postcoitum (p.c.), testes, and ovaries dissected from fetuses on Days 14.5 p.c. to 20.5 p.c. and testes obtained on Days 3, 5, and 7 postpartum were fixed in Bouin's solution and processed for immunocytochemistry, In all samples of fetal testis, SP-HSD was detected on Day 14.5 p.c. and immunoexpression of P450(c17) appeared one day later on Day 15.5 p.c. Thereafter, immunoexpression of both enzymes remained intense throughout gestation and postnatally, In contrast, immunoexpression of LH receptors was detectable only front Day 16.5, when a few weakly positive cells were present, hut it became more intense one and two days later, Similar to the immunostaining for 3 beta-HSD and P450(c17), immunostaining for LH receptor remained strong throughout gestation and during the first 7 days of postnatal life. No immunoexpression of any of the three proteins studied was detected in the fetal ovary at any age, These data show very early immunoexpression of 3 beta-HSD, which was detected one day before he reported tart of steroid production by the fetal Leydig cells, in contrast immunoexpression of LH receptors was evident only, after immunoexpression of both the steroidogenic enzymes studied had became apparent and after the reported start of steroidogenesis, which Is consistent with the theory that onset of steroidogenesis in the fetal rat testis is an LH-independent process.