The relation between induced reciprocal translocations and cell killing of mouse spermatogonial stem cells after combined treatments with hydroxyurea and X-rays.

The induction of reciprocal translocations in mouse spermatogonial stem cells, visualised in dividing primary spermatocytes, was studied after combined treatments with hydroxyurea (250 and 500 mg/kg) and X-rays (6, 8 and 9 Gy). The time intervals between the 2 treatments were 16 h (leading to extremely high cell killing) and 48 h (giving rise to less killing than irradiation alone). Comparison of the observed frequencies of translocations with reported data on stem cell killing (de Ruiter-Bootsma and Davids, 1981) show that the ratio between the probabilities that a radiation-induced basic lesion kills a cell or produces a translocation, theoretically calculated by Leenhouts and Chadwick (1981) to be about 10, can indeed be confirmed experimentally.