Effect of different 90Sr doses on the microscopic structure of foetal mouse ovaries

Pregnant CBA-mice were injected with different doses of 90Sr on the 19th day post coitum. The doses ranged between 11.1 and 370 kBq (0.3-10.0 muCi) per animal. The ovaries of the in utero treated females were analysed when the animals were 28, 56 or 84 days old, respectively. The effect of the nuclide was expressed as a reduction of the number (frequency) of cells in different stages of ovarian development in a comparison between 90Sr treated animals and untreated controls. The injury (reduced number of cells) was strongly correlated to log dose. The most radiation sensitive stage (the naked oocytes) was clearly affected even at the lowest dose level. The different ovarian 90Y/90Sr ratios in litters and their mothers are discussed.