MICRONUCLEI AND 3AB INDEX IN HUMAN AND CANINE LYMPHOCYTES AFTER IN-VITRO X-IRRADIATION

The comparative study of different species could be of interest, both applied and pure, to the field of cytogenetic damage induced by genoto xic agents. For as accurate as possible an evaluation of the inter-spe cies response differences to radiation, we have carried out a comparis on between the behaviors of human and canine lymphocytes, using the mi cronucleus assay (MN test) according to the cytokinesis-block method. Up to 4 Gy doses, canine lymphocytes have been found to be about three times more radiosensitive than human lymphocytes, due to blastization inhibition (binucleation failure), and, for 1 and 2 Gy doses, about 1 .3 times more radiosensitive, due to MN yields. We discuss whether the differing chromosome number (dog 78 and man 46) could have any effect on the cytogenetic response. 3-Aminobenzamide, which inhibits poly(AD P-ribose)polymerase activity, is able to increase the genotoxic effect of X-rays in human lymphocytes, with a different response at the indi vidual level. The same phenomenon with the same characteristics is als o found in canine lymphocytes at the inter-individual level. Our in vi tro radiobiological study confirms that the cytogenetic response obtai ned in blood from selected breeds of mammalian species can be utilized for applications in environmental studies.