title: Dose response at low doses of X-irradiation and MMS on the induction of micronuclei in mouse erythroblasts.
abstract: The test of induced micronuclei in erythrocytes of mammalian bone marrow constitutes, because of its high experimental resolution power, a suitable method for the screening of induced chromosomal lesions at very low dosages of chemicals or irradiations. This test was used for a comparative investigation of the effect of low dose levels of X-irradiation and of the alkylating agent methyl methanesulphonate (MMS). The dose-effect curve of X-irradiation indicated a deviation from linearity at 10 rad, showing a significantly stronger effect than expected on extrapolation from the control to 100 rad. This deviation from linarity, however, only appeared at a low dose rate (18 R/min), whereas a linear dose-effect relation was indicated with a high dose rate (95 R/min). Experiments at 10 rad with different dose rates at two different current potentials suggested that this effect of the dose rate is more pronounced with soft than with hard X-irradiation. The induction of micronuclei with MMS follows a drastically different dose-effect curve as compared with X-irradiation. The relative efficiency of the treatment is lowest at low concentrations, presumably as a result of the efficient repair process at such dose levels. Simultaneous treatment with X-rays and MMS at low dose levels only resulted in an additive effect. This suggests that X-irradiation does not interfere with the repair process operating with MMS. The difference in the dose-effect relations of X-irradiation as compared with MMS may be brought back to the fact that X-rays, in contrast with MMS, produce double-strand breaks.
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000648:ultrastructure*; D001854:Bone Marrow Cells; D002467:Cell Nucleus / Q000648:ultrastructure; D002869:Chromosome Aberrations; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004900:Erythroblasts / Q000187:drug effects / Q000528:radiation effects; D005821:Genetic Techniques; D008297:Male; D008698:Mesylates / Q000494:pharmacology*; D008741:Methyl Methanesulfonate / Q000494:pharmacology*; D051379:Mice; D008808:Mice, Inbred CBA; D014965:X-Rays
chemical_list: D008698:Mesylates; D008741:Methyl Methanesulfonate