Abstract 20

It has been proposed that estrogens might play a negative feedback role in the regulation of androgen biosynthesis in the testis. The expresion of the CYP19 gene in the human prepubertal testis has not been studied but is has been reported that aromatase is present in human Leydig cells. By RT-PCR we have studied the presence of CYP19 mRNA in 7 prepubertal testis (0.08 to 7 years old) and in 1 pubertal testis (15-y-old) in gonads collected at necropsy. Furthermore, testicular cells from 12 prepupertal patients (0.05 to 7 years old) and from 2 pubertal patients (15-y-old) were maintained in culture during 2 days in the presence of 10% fetal bovine serum, followed by 4 additional days in serum-free medium. The secretion of testosterone and estradiol was measured by RIA in conditioned media at the end of days 2, 4 and 6 of the 12 prepubertal cell cultures, while CYP19 mRNA was determined, on day 6, in cell extracts of the 14 cultures. No CYP19 mRNA was detected neither in the 7 prepubertal testicular tissues nor in the 12 prepubertal testicular cells on day 6. However, it was detected in the pubertal testicular tissue and in the 2 pubertal testicular cells. Prepubertal testicular cells strongly increased testosterone secretion between days 2 and 6 of culture, presumably under the influence of serum components. Unexpectedly, estradiol secretion was detected on day 2, in an amount equimolar to that of testosterone, but it became undetectable on days 4 and 6. It is concluded that human prepubertal testicular cells at rest do not express the CYP19 gene. However, in an in vitro model of onset of spermatogenesis, a transient stimulation of estradiol secretion was found. It is suggested that at initiation of steroidogenesis, there is a modulatory mechanism with a transient regression of the CYP19 gene to facilitate testosterone biosynthesis. In advanced puberty and in adult subjects, the expression of the CYP19 gene is reestablished.