Induction of solid tumours in the Swiss albino mouse by low-dose foetal irradiation

To study the tumourigenic effect of prenatal low-dose gamma-irradiation in the mouse.

Pregnant Swiss albino mice were exposed to 0.1-1.5 Gy gamma-radiation on days 14 or 17 of gestation. The F1 offspring were observed up to 18 months of age. All the mice were killed at 18 months and the incidence of tumours in different organs was recorded.

Exposure to doses from 0.1 to 1.5 Gy on days 14 or 17 of gestation produced a linear-quadratic dose-dependent increase in tumour incidence in adult F1 mice. The main organs affected were the ovary, uterus, liver and spleen. The highest incidence was observed in the ovaries, which was significantly higher than spontaneous incidence, even at 0.25 Gy. In other organs the tumour incidence was not significant compared with controls at doses < 0.5-1.0 Gy. Tumours in the ovary and uterus developed at an earlier age than in the liver and spleen.

Exposure to gamma-radiation < 1.0 Gy at the foetal period (days 14 or 17 of gestation) can cause induction of tumours in the Swiss albino mouse. The carcinogenic effect, particularly on the ovary among the female mouse, is detectable after low-dose foetal irradiation.