Reciprocal translocations in germ cells of male mice receiving external γ-irradiation

Abstract

Data reported in the literature up to 1985 on reciprocal translocation induction in male mouse germ cells by external γ-ray doses ranging from 0.5 to 6.0 Gy delivered at fixed dose rates were analyzed. On the assumption of a non-threshold linear dose response, zero effect at zero dose, and a center of distribution lying on an approximately straight line, calculations were made of linear regression coefficients. These coefficients ( b), as a function of the dose rate ( P), were well fitted by two straight lines: b = (3.15 + 0.59 log P) × 10 −6 for dose rates from 0.01 to 0.1 mGy/min; and b = (7.52 + 3.86 log P) × 10 −6 for dose rates ranging from 0.06 to 1.2 × 10 3 mGy/min. The intersection point of these two lines determined the so-called threshold level of the dose rate, namely, 4.6 × 10 −2 mGy/min, at which the effectiveness of external γ-irradiation is not expected to exceed 2.36 × 10 −6/mGy. In addition, experiments were undertaken in which yields were recorded of reciprocal translocations in germ cells of male mice exposed to 0.9 Gy of γ-radiation at dose rates ranging from 6.14 × 10 −3 to 6.14 × 10 2 mGy/min (6 levels); comparisons were made with data published up to 1985 from similar studies using other fixed doses. To do this, translocation yields were expressed as relative yields ( F) and their relationship to the dose rate ( P) for the individual fixed doses was represented by an equation of the type: F = α + β log P. For most of the equations, the regression coefficients were in good agreement and a single relationship was obtained to represent them. From the analysis performed it follows that, within the 0.6–6.0 Gy dose range, the pattern of the F vs. P relationship is unaffected by the dose. This supports the initial assumption that for the dose range up to 6.0 Gy the dose response for the reciprocal translocation yield is a non-threshold straight-line relationship.