FLOW-CYTOMETRIC IDENTIFICATION AND FOLLOW-UP OF MICE EXPOSED TO X-IRRADIATION - EVALUATION OF A MODEL SYSTEM

An experimental model system is presented that allows the identificati on and follow-up of mice exposed to ionizing radiation using flow-cyto metric measurements of peripheral blood cells. In an experiment, prope rties of peripheral blood cells were analysed with flow cytometry for a rapid identification of individuals exposed to radiation. Individual s were then followed longitudinally in an attempt to identify those de veloping neoplasias. Male CBA mice, 25 days old, were subjected to fra ctionated x-irradiation (4 x 1.31 Gy) to induce haematopoietic maligna ncies. By repeated blood sampling followed by flow cytometry, frequenc ies of micronucleated erythrocytes and of proliferating nucleated cell s were determined. Neoplasias were diagnosed by histopathology. Five d ays after the end of radiation exposure, increased frequencies of prol iferating cells, polychromatic erythrocytes and micronucleated normoch romatic erythrocytes clearly distinguished the exposed group from the control group. Increased cell prolife ration in peripheral blood cells could be used to identify animals with manifest tumours, although the se animals were at a late stage of tumour development. Animals with th ymic lymphoma (not generalized) could not be identified with the flow- cytometric parameters used. We consider that this model system has a p otential use when a small number of risk individuals need to be identi fied and monitored within a large population.