EFFECTS OF EPIDERMAL GROWTH-FACTOR ON THE GROWTH AND DIFFERENTIATION OF CULTURED MOUSE OVARIAN FOLLICLES

The aim of this investigation was to determine the influence of epider mal growth factor (EGF) on follicular growth and steroidogenesis in mi ce. Follicles were cultured in medium containing human recombinant EGF at concentrations of 1-20 ng ml(-1). Oestradiol production was assaye d immunoenzymatically, and growth was measured by recording follicle d iameter daily and by analysing the total DNA content of follicles. The effect of EGF on cumulus-oocyte complexes isolated from cultured foll icles was also assessed. Results showed that EGF inhibited oestradiol production in a dose-dependent manner, but had no mitogenic effect. De spite almost complete inhibition of oestradiol production at concentra tions of EGF greater than or equal to 10 ng ml(-1), follicles were sti ll able to achieve preovulatory size and morphology, although the inci dence of atresia was increased over controls. Conversely, at a concent ration of only 1 ng EGF ml(-1), a significantly greater number of foll icles reached the Graafian stage compared with control follicles. Cumu lus expansion and meiotic maturation by isolated cumulus-oocyte comple xes from cultured follicles was dramatically stimulated in the presenc e of EGF and FSH, but not by FSH alone. These findings suggest that EG F may have a modulatory effect on oestradiol production in vivo, and t hat follicular growth and differentiation may be uncoupled from steroi dogenesis. Finally, ovulatory changes in the cumulus-oocyte complex ma y require the presence of this factor.