Whole-body or isolated ovary (60)Co irradiation: effects on in vivo and in vitro folliculogenesis and oocyte maturation.

For the first time, the effects of low doses of gamma-radiation were studied on folliculogenesis and on isolated oocytes. After irradiation of adult mice, even at the lowest dose, a drastic loss of primordial follicles was observed in serial sections of ovaries, with, in opposite, no effect on the other follicle stages. Moreover, oocytes freshly recovered from the largest antral follicles of irradiated adult ovaries exhibited significantly less regular Ca(2+) oscillations than controls. Finally, in vitro folliculogenesis demonstrated a smaller diameter of preantral follicles recovered from irradiated juvenile ovaries compared to control, and an increase in follicle atresia. Further on, PLC-beta1 localization was not affected in the enclosed oocytes whereas chromatin configuration revealed that a quarter of them had prematurely resumed meiosis or was fragmented. These results raise the question of the risk of genetic and teratogenic effects on women submitted to chronic exposure even of very low radiation.