Effects of bovine follicular fluid and partially purified bovine inhibin on FSH and LH release by bovine pituitary cells in culture.

We have established a dispersed bovine pituitary cell culture system to study the effects of charcoal-extracted bovine follicular fluid (BFF) or bovine inhibin, partially purified by immunoaffinity chromatography (IPI), on the spontaneous release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Pituitary cells were plated at 0.25, 0.5 or 1 x 10(6) viable cells/well (c/w) and incubated for 48 h. The medium was replaced and BFF (0, 0.54, 2.7, 13.7, 68.7 or 343.5 micrograms protein) or IPI (0, 0.01, 0.06, 0.29, 1.45 or 7.25 micrograms protein) added to the cultures and the incubation was continued for 48 h. Concentrations of FSH and LH in spent medium were determined by RIA and data analyzed by ANOVA with means compared by Student-Neuman-Keuls (SNK) test. We have shown an increase in spontaneous FSH and LH release attributable to both number of bovine pituitary cells plated and to the length of incubation. The addition of BFF reduced spontaneous FSH release over 48 h incubation. The dose-dependent inhibition curves observed in culture in which different numbers of cells were plated, indicates that inhibition was greater when 1 x 10(6) c/w were plated compared to 0.25 or 0.5 x 10(6) c/w. Bovine follicular fluid at 0.45 micrograms of protein (equivalent to 0.01 microliters of BFF) incubated with 1 x 10(6) c/w, suppressed FSH release by 10.6% compare to control. Maximal suppression of 34.1% was obtained with 50 micrograms (equivalent to 1.56 microliters of BFF). Immunopurified bovine inhibin at 1.45 micrograms tended to suppress FSH release and at 7.25 micrograms significantly reduced FSH release. Neither BFF nor IPI had a measurable effect on LH release. We conclude that BFF and IPI suppress the spontaneous release of FSH from bovine pituitary cells in culture in a dose-dependent manner, without concomitant suppression of LH release.