In vitro effects of germ cells on the secretory activity of Sertoli cells recovered from rats of different ages.

Indirect (hypotonically treated culture) and direct (coculture) approaches were used to study the influence of germ cells on androgen-binding protein (ABP) and 17 beta-estradiol secretion by Sertoli cells prepared from 10-, 15-, 20-, and 45-day-old rats. Using these approaches, the mechanisms that govern Sertoli cell-germ cell membrane recognition were shown to be unaltered by the hypotonic treatment, to vary with the age of the Sertoli cell donors, and to be FSH/(Bu)2cAMP dependent in the younger animals (10-20 days old). Hypotonic treatment had no effect on estradiol levels at all ages studied, but resulted in a marked fall of ABP production by Sertoli cells from 20 days onward. However, the relative stimulation of ABP induced by FSH/(Bu)2cAMP (ABP levels in FSH/(Bu)2cAMP/hypotonically treated Sertoli cell cultures vs. ABP in hypotonically treated cultures) was markedly increased at 20 and 45 days, indicating that germ cells influence Sertoli cell responsiveness to FSH/(Bu)2cAMP. The addition of crude germ cell preparation to the Sertoli cell cultures stimulated ABP and inhibited estradiol levels at all ages studied. Moreover, the addition of germ cells to hypotonically treated cultures induced a decrease in the relative ABP response to FSH and (Bu)2cAMP, thus confirming (see above) that germ cells may be involved in the mechanism of Sertoli cell refractoriness to FSH that occurs with advancing age in the rat. Germ cell-stimulated ABP production was higher in adult Sertoli cells than in immature cells. That Sertoli cell responsiveness to germ cells varies with age is further supported by the data showing that whereas spermatocytes stimulated ABP and inhibited estradiol productions at all ages studied, early spermatids only influenced these parameters from 20 days onward. It is concluded that germ cell control over Sertoli cell function in vitro may be of important physiological significance during Sertoli cell maturation in mammals.