Minimal quantities of FSHβ subunit are released by rat anterior pituitary cells in primary culture

FSHβ in the medium and extracts of cultured rat anterior pituitary cells was quantitated with a heterologous radioimmunoassay utilizing anti-rFSHβ and hFSHß as the standard and tracer. After 4 days in culture, extracts were prepared from washed cells, cells incubated for 6 h or 24 h in fresh medium or cells incubated for 6 h in the presence of 10^-7 M GnRH. FSHß/rFSH molar ratios were approximately 0.05, 0.04, 0.21 and 0.35, respectively. The elevation in FSHß/rFSH molar ratios in 24 h basal and GnRH-teated cultures was due in part to an increase in intracellular FSHß. Both unstimulated and GnRH-treated cultures contained non-detectable quantities of FSHß in the medium (< 0.063 ng/100000 cells; FSHß/rFSH molar ratio < 0.024). Thus, it appears that cultured rat anterior pituitary cells contain a small amount of uncombined FSHß but that minimal quantities are released. Furthermore, GnRH may increase intracellular quantities of FSHß but does not induce its release.