Effects of FSH and testosterone on highly purified rat Sertoli cells: inhibin alpha-subunit mRNA expression and inhibin secretion are enhanced by FSH but not by testosterone.

The effects of FSH and testosterone on inhibin mRNA expression and inhibin production by highly purified Sertoli cell preparations were examined. Sertoli cells were isolated from testes of 22-day-old rats by sequential trypsin, collagenase and hyaluronidase treatments, with subsequent osmotic shock treatment on day 3 of culture. Contamination by peritubular and germ cells was less than 0.5 and 1-3% respectively. Intracellular and secreted inhibin levels were measured by radioimmunoassay, using Sertoli cells which were incubated for 24 h in the absence or presence of FSH and testosterone from days 4 to 5 of culture. FSH stimulated the cellular inhibin content and the secreted inhibin level by four- and sevenfold respectively, with a half-maximal effective dose of 5-50 ng/ml. Under the present incubation conditions, testosterone (1 mumol/l) had no effect on immunoreactive inhibin levels in either the presence or absence of FSH. Similarly, the expression of inhibin alpha-subunit mRNA was increased following FSH stimulation, whereas testosterone had no effect. The expression of inhibin beta B-subunit mRNAs was not influenced by FSH or testosterone. It is concluded that highly purified Sertoli cell preparations, with a very low number of peritubular or germ cells, are fully responsive to FSH with respect to inhibin mRNA expression and inhibin production.