DOSE DEPENDENCE OF RADIATION-INDUCED MICRONUCLEI IN CYTOKINESIS-BLOCKED HUMAN-LYMPHOCYTES

Following selection of appropriate culture conditions, various experim ents were conducted to evaluate the suitability of the micronucleus as say in cytokinesis-blocked lymphocytes for biological dosimetry purpos es. A dose-effect relationship was determined, based on the frequency of micronuclei induced by various doses of Co-60 gamma-rays. The data were best fitted to a linear-quadratic model. To validate the system, an attempt was made to estimate unknown dose levels from the yield of micronuclei, by inverting the derived dose-response function. It was c oncluded that the assay provides a valid approach for dose assessment. The size of radiation-induced micronuclei was measured in relation to the dose. A significant difference in the proportion of large micronu clei between high and low doses was observed. The chromosomal composit ion of micronuclei, detected by immunofluorescent staining of kinetoch ores, showed that only a small proportion of micronuclei contains kine tochore. The possible contribution of various mechanisms for the forma tion of large radiation-induced micronuclei is discussed.