Effect of 90Sr on ovaries of foetal mice depending on time for administration during pregnancy.

Pregnant CBA-mice were injected with 3.7 x 10(5) Bq (10 muCi) 90Sr on the 8th, 11th, 13th, 16th or 19th day post coitum. The effect on the ovaries in the intrauterine-treated animals was analysed on the 28th, 56th and 84th day post partum. The result was expressed as a comparison between the number of cells in different stages of development in the treated individuals compared to untreated control animals. The reduction of the number of cells in the ovaries was strongly correlated to the time of administration of the nuclide with a more increased effect the later during foetal development the contamination occurred. The oocytes and primordial follicles were the most radiation sensitive stages. The remaining cells in the ovaries are supposed to form a numerically reduced pool of functionally normal cells.