Estradiol regulation of follistatin and inhibin α- and β(B)-subunit mRNA in avian granulosa cells

Abstract

Estradiol modulation of granulosa cell growth and regulation of follistatin and inhibin α- and β(B)-subunit mRNA were investigated in cultured chicken granulosa cells. Granulosa cells were isolated and pooled according to size from the F4 + F5, small yellow (SYF), and large white (LWF) follicles. Isolated and dispersed granulosa cells were then cultured in the absence or presence of 1 x 10-5 M 17 β-estradiol. In Experiment 1 (n = 4 replications) the effect of estradiol on the growth of granulosa cells from the different-sized follicles was examined at 24 and 48 h of culture. Untreated and treated granulosa cells from all three follicle sizes proliferated during culture, and cell viability for all cultures was over 95% throughout the experiment. After 48 h the untreated cultures for all follicle types had 1.6 to 2.2 times (P < 0.05) more cells than the estradiol-treated cultures. In Experiment 2 (n = 3 replications), the cultures were terminated at 4 and 24 h after plating. Follistatin mRNA levels were higher in estradiol-treated cells at 24 h in F4 + F5 follicles, at 4 and 24 h in the SYF, and at 4 h in the LWF. β(B)-subunit mRNA levels were also increased by estradiol at 4 h in F4 + F5 cells and at 4 and 24 h in the LWF. Steady state mRNA levels for the α-subunit were higher (P < 0.05) in estradiol-treated cultures at 4 and 24 h in F4 + F5 follicles and at 24 h in the SYF. Immunoreactive α-subunit protein, however, was not increased by estradiol treatment. Thus, whereas estradiol inhibited granulosa cell growth, it exerted a generally stimulatory effect on the expression of FS and the inhibin α- and β(B)-subunit mRNA. (C) 2000 Academic Press.