TRANSFORMING GROWTH-FACTOR BETA-STIMULATING AND FOLLICLE-STIMULATING-HORMONE PROMOTE RAT GRANULOSA-CELL PROLIFERATION

Rat granulosa cells isolated from the ovaries of diethylstilbestrol-primed immature rats were treated with estrogen, FSH, and growth factors to determine those factors that were required to promote DNA synthesis. Estrogen and FSH, previously shown to stimulate the incorporation of [3H]thymidine into rat granulosa cell DNA in vivo, were ineffective in vitro. Epidermal growth factor, insulin-like growth factor 1 (IGF1), and fibroblast growth factor did not influence DNA synthesis whereas transforming growth factor .beta. (TGF.beta.) alone had a significant effect. Neither estradiol-17.beta. (5 .times. 10-8-5.times.10-6 M) nor IGF1 augmented the actions of TGF.beta. and FSH. FSH did not influence the actions of epidermal growth factor of IGF1 but dramatically augmented the effect of TGF.beta. on DNA synthesis. FSH and TGF.beta. also stimulated [3H]thymidine incorporation into the DNA of granulosa cells isolated from immature rats not treated with diethylstilbestrol. The increase in [3H]thymidine incorporation into DNA stimulated by TGF.beta. and FSH resulted subsequently in an increase in cell number. The response of the cells to TGF.beta. in the presence of a constant level of FSH (10 ng/ml) was dose dependent, 2.5 ng/ml being the minimal effective concentration. In the presence of antibody specific for TGF.beta. the bioactivity of the TGF.beta. was neutralized indicating that the growth promoting activity was due to TGF.beta. and not due to contaminants. In this paper, we have shown that the combined actions of FSH and TGF.beta. influence DNA synthesis and the proliferation of rat granulosa cells. Interactions between FSH and TGF.beta. may be important in regulating aspects of rat granulosa cell growth in addition to exerting pronounced effects on cytodifferentiation.