Paracrine regulation of FSH by follistatin in folliculostellate cell-enriched primate pituitary cell cultures.

Primary pituitary cell cultures are an important tool for understanding pituitary hormone gene expression. In the course of study of pituitary cell cultures from nonhuman adult male primates, pituitary secretory cells were noted to be rapidly overgrown by epithelioid cells with the morphological, immunocytochemical, and proliferative characteristics of folliculostellate cells. Using competitive RT-PCR assays, follistatin mRNA levels were found to increase 4-fold as folliculostellate cells proliferated with time in culture, whereas FSH-beta mRNA and FSH secretion were suppressed. Follistatin gene expression was stimulated by activin-A and pituitary adenylate cyclase-activating polypeptide but not by [D-Trp(6)]-GnRH ethylamide. Testosterone (T) also increased follistatin mRNA levels and follistatin protein secretion. FSH-beta mRNA was stimulated by [D-Trp(6)]-GnRH ethylamide and activin but was suppressed by T. The reciprocal relationship between follistatin and FSH-beta mRNA levels as folliculostellate cells proliferate with time in culture implies a role for folliculostellate cells in the follistatin-activin system in primates. The actions of GnRH and T on follistatin and FSH-beta mRNA levels in these cultures were opposite to effects observed in pituitary cultures from rats and identify species differences in the control of FSH production that may be folliculostellate cell-related.