[Paracrine regulation of Leydig cell aromatase in the rat: development with age].

The paracrine regulation of rat testicular aromatase activity has been studied at various ages (20, 30, 45, 55, 70, 240 days); seminiferous tubule culture medium (STM) have been prepared at the above ages and added (40%, v/v) to the Percoll purified Leydig cells (150,000) for 5 h at 32 degrees C in presence or absence of oLH (25 ng/ml). In 20 day-old rat, the basal oestradiol-17 beta (E2) output is low (20 pg/10(6) Leydig cells), then gradually increases until day 70 (280 pg) without any change at 240 days (260 pg). In presence of oLH, a 2 fold increase of E2 output is observed whatever the age and the addition of STM further enhances both the basal (21-41%) and the LH-stimulated (14-65%) E2 syntheses. In conclusion, the Leydig cell aromatase activity, is in part regulated by STM factors, mainly after puberty. From 20 days onwards, it is noteworthy, that the Leydig cell testosterone (T) synthesis is highly stimulated by oLH (10 fold) and the addition of STM further increases T outputs (2 fold) which brings about a high intratesticular T level necessary for development of spermatogenesis.