[Chromosome hyper-radiosensitivity in mice at the end of pregnancy]

Irradiation of mice with 2 Gy of gamma-rays at various times of pregnancy induces a threefold increase in the rate of chromosome breaks in spontaneously dividing bone marrow cells from the 16th to 19th days. This high sensitivity disappears shortly after delivery, and it is even possible that a hyposensitivity develops at this time. The causes of this phenomenon remain unknown, but since it occurs shortly after the high increase of oestrogen and progesterone hormones, a direct relationship may exist.