Regulation of the aromatase gene expression in mature rat Leydig cells

Besides gonadotiophins and testosterone, numerous intratesticular factors, and among them estrogens play a crucial role in the regulation of spermatog enesis in the mammalian testis. The ability of the male gonad to convert an drogens into estrogens is well known; the microsomal enzymatic complex invo lved in this transformation named aromatase, is composed of a specific cyto chrome P450 aromatase (P450arom) and a ubiquitous reductase. Using a highly specific reverse transcription polymerase chain reaction (RT-PCR) method, we have measured the amount of P450arom mRNA in purified rat Leydig cells s ubmitted to different treatments during 24 h. In parallel, the estradiol ou tput was determined by RIA. Whatever the concentrations of testosterone use d las substrate of aromatase activity), we noted an increase of the estradi ol production, the maximum being obtained for 200 ng/ml (28%). Related to t he P450arom mRNA levels, a decrease was first observed for 50 and 100 ng/ml of testosterone then an increase (20%) for the higher doses (200-500 ng/ml ). The addition of oLH (0.1-50 ng/ml) to the Leydig cells culture medium in duced a dose-related increase of estradiol output till 10 ng/ml. For 50 ng/ ml, a decrease was observed. Dealing with the mRNA levels, we first recorde d a diminution For 0.1 - 1 ng/ml of oLH, which was abolished by the additio n of testosterone. Then the mRNA levels were increased and reached a maximu m for 5-10 ng/ml of oLH (35 and 50% respectively, in absence and ill presen ce of testosterone). The addition of oLH (50 ng/ml) induced a large augment ation of the quantity of P450arom mRNA (1.9 and 2.1-fold, respectively, in absence or in presence of testosterone). DbcAMP mimicked the effects of oLH . From these data, we confirm the presence of cAMP response-like elements ( CRE) and the existence of androgen responsive elements (ARE) sites on the P 450arom gene in rat Leydig cells. (C) 2001 Elsevier Science Ireland Ltd. Al l rights reserved.