Development and cellular localization of rat testicular aromatase activity.

Oestradiol secretion by isolated Leydig cells, Sertoli cells, myoid cells, germinal cells and liver cells from rats of different ages was measured by a validated radioimmunoassay technique. All cells, except germinal cells and liver cells, produced oestradiol when incubated in the presence of testosterone. Sertoli cells from 7- and 10-day-old rats and from prenatally irradiated adult rats were 7 times more active than cell preparations from 15--50-day-old rats. The oestradiol production in Sertoli cells prepared from 7--25-day-old rats could be stimulated with FSH. Oestradiol production by isolated Leydig cells from mature animals was 3--4 times greater than that with preparations from immature animals. LH had no effect on oestradiol production, but testosterone production was stimulated more than 5-fold. The oestradiol production by the isolated cells was affected by culture time, the presence of fetal calf serum in the culture medium and incubation temperature. During a culture period of 6 days oestradiol production by immature Sertoli cells increased more than 5-fold and that by Leydig cells decreased to about 10%. Oestradiol levels in testes from 10--50-day-old rats were approximately 20% of those in testes from 7-day-old animals.