EFFECTS OF PHYTO-OESTROGENS ON PROGESTERONE SYNTHESIS BY ISOLATED BOVINE GRANULOSA CELLS

Abstract

The effects of phyto-oestrogens on progesterone synthesis by isolated bovine granulosa cells in vitro were assessed. Various concentrations (0·037–3700 nmol/l) of biochanin A, genistein or oestradiol were added to cultures of bovine granulosa cells and the consequent changes in progesterone synthesis were measured. The effects of alkali-soluble extracts of Rhodes grass (Chloris gayana) and fodder beet (Beta vulgaris, var.) were also examined. Another series of experiments tested the effects of genistein and oestradiol on the increase of progesterone synthesis brought about by the addition of LH to the culture medium. It was found that biochanin A and genistein increased progesterone synthesis by 40–50% when added in concentrations of 3·5 and 185 nmol/l respectively. At higher concentrations progesterone synthesis declined and was significantly (P < 0·05) inhibited at concentrations of phyto-oestrogens greater than 176 nmol/l for biochanin A and 1850 nmol/l for genistein. Oestradiol showed similar effects: maximum stimulation of progesterone secretion occurred in the presence of 0·184 nmol/l; inhibition was found with concentrations of greater than 1·84 nmol/l. Extracts of Rhodes grass but not of fodder beet also showed biphasic effects. Both genistein and oestradiol in high concentrations (3700 and 3671 nmol/l respectively) inhibited the increase in progesterone synthesis provoked by LH. The data indicated that phyto-oestrogens, like oestradiol, have a dose-related, biphasic effect on steroidogenesis in the isolated bovine granulosa cell system.