Influence of 90Sr-contaminated milk on the ovaries of foetal and young mice.

A dose of 185 kBq (5 microCi) 90Sr was intravenously injected into pregnant CBA-mice on the 19th day post coitum. Four groups of female young were examined when aged 56 days: (1) non-contaminated females (controls), (2) only exposed in utero, (3) only having suckled contaminated milk and (4) exposed to 90Sr in utero and having suckled contaminated milk. The effect of the nuclide was expressed as a comparison of the number of remaining cells in the ovaries, totally and in different stages of development, between 90Sr-contaminated young and controls. Young mice that suckled contaminated milk had a reduced number of cells compared with the controls. The ovaries of in utero contaminated females were injured to a less severe degree if the individuals were given noncontaminated milk, compared with those suckling contaminated dams. Minute changes of the body burden of 90Sr were especially reflected in the number of young oocytes, being the most radiation sensitive stage during the ovarian development.