Influence of germ cells on Sertoli cell secretory activity in direct and indirect co-culture with Sertoli cells from rats of different ages.

We examined the effect of direct and indirect Sertoli-germ cell co-culture on androgen binding protein (ABP) and transferrin (TRF) secretion by Sertoli cells (Sc) from 10-, 18-, and 26-day-old rats. Addition of germ cells (Gc), mainly (greater than 80%) pachytene spermatocytes, directly to Sc monolayers enhanced basal and follicle-stimulating hormone (FSH) + testosterone-stimulated ABP and TRF secretion at all three ages. When the Gc were co-cultured indirectly with Sc (separated by a Nucleopore filter), only 50% of the direct stimulatory effect was found at 18- and 26-day-old groups, whereas no difference between direct and indirect co-culture was noted with Sc from 10-day-old rats. With 18- and 26-day-old rat Sc, the Gc effect on ABP and TRF secretion declined after 6 days of Sc culture, reaching the level of Sc-only cultures after 10 days, whereas the direct effect was maintained throughout the entire culture period. With Sc from 10-day-old animals, both direct and indirect effect of Gc decreased after 6 days but the levels of ABP and TRF secretion remained above those of Sc-only cultures. The viability and number of Gc in indirect co-cultures were maintained significantly higher than in Gc-only control cultures. The direct and indirect Gc effect was completely reversed 48 h after the Gc were removed from Sc cultures of 18- and 26-day-old rats, whereas in Sc cultures from 10-day-old rats 40% of the stimulatory effect remained after 48 h of Gc removal. We conclude that Gc can influence Sc secretory activity through both direct contact and some released factor(s). These two pathways may have different relevance at different ages during sexual maturation.