The Effects of Micronuclei with Whole Chromosome on Biological Dose Estimation

The total micronucleus (MN) assay has been used for purposes of biological dosimetry for many years. The variable spontaneous incidence of micronuclei in peripheral blood lymphocytes affects the sensitivity of biological dose estimations at low doses. It has been suggested that this problem could be solved by using the micronuclei-centromere assay.In this study, Co-60 gamma ray dose response curves for micronuclei (MN) and micronuclei without centromeres (MNC-) in the rangeof 0-5.0 Gy were established using a pancentromeric FISH probe on cultured binucleate lymphocytes from 2 donors. There were no significant inter-donor differences in the dose responses for either MN or MNC-. The relative proportions of MN that contained centromeres (MNC+) decreased with radiation dose, which is in line with the proposition that radiation predominately cause schromosomal breakage rather than whole chromosome loss. The ß coefficients of MNC- curves decreased to 62% of the values fortotal MN whilst the ß coefficients were unchanged.MN and MNC+ frequencies of 60 control smoker and 40 non-smoker donors were also compared. No effect of smoking was observed. However the MNC+ spontaneous frequencies showed an age and gender effect with the highest frequencies in older women.