Dose-effect relationship for X-ray-induced translocations in spermatogonia of normal and T70H translocation heterozygous mice.

The induction of reciprocal translocations in stem cell spermatogonia was studied in normal mice and T70H translocation heterozygotes using spermatocyte analysis many cell generations after irradiation. Dose-response relationships were constructed employing acute X-ray exposures of 1-10 Gy. The obtained results confirmed our earlier observations that T70H heterozygous mice were overall less sensitive to the induction of translocations compared to normals. The shape of the dose-response curve for T70H heterozygotes was also clearly different from normal mice. No simple correlations between cell killing, measured as testis weight loss, and observed frequencies of chromosomal anomalies could be established. In general, selective elimination of translocation carrying stem cells of T70H heterozygotes seem to be mainly responsible for the differences in induction pattern between the two types of mice.