Cytogenetic effects of environmental mutagens in mammalian cells and the extrapolation to man

Abstract

Summary In order to extrapolate from cytogenetic data obtained with laboratory animals, with the intention of making an estimate of the genetic hazard of ionizing radiation, and possibly chemical mutagens, to man, several factors have to be taken into consideration. This paper represents an attempt to account for such factors and to make such an estimate. It is shown, for the mouse, Chinese hamster, and marmoset, that the yield of chromosome aberrations induced in peripheral leukocytes by X-rays was the same whether the cells were exposed in vivo or in vitro . It is also demonstrated that the yield of dicentric aberrations (asymmetrical translocations) varied from species to species, and that the yield was proportional to the number of chromosome arms available for translocation production, such that man, with 81 chromosome arms, was twice as sensitive as the mouse, which has 40. The yield of deletions did not vary from species to species. The yield of reciprocal translocations induced in spermatogonial stem cells by X-rays, and observed in primary spermatocytes, was measured in the mouse, Chinese hamster, guinea pig, and marmoset. It was found that the yield of reciprocal translocations was 0.25–0.30 of that assumed to be induced in peripheral leukocytes. It was also noted that the yield was here also related to the effective chromosome arm number. Using these and other data, it is proposed that the dicentric yield in human leukocytes can be corrected by a factor of 0.03–0.04 in order to derive an estimate of the recovered reciprocal translocations in the F 1 of irradiated males.