MEASUREMENT OF MICRONUCLEI BY CYTOKINESIS-BLOCK METHOD IN BOVINE LYMPHOCYTES

The present study was carried out in order to set up a standardized qu antitative assay for spontaneous micronuclei in bovine lymphocytes. Fo r this purpose the cytokinesis-block micronucleus (MN) method, origina lly proposed by Fenech and Morley (1985) for human lymphocytes, was ap plied to peripheral blood lymphocytes of 20 healthy cows of Italian Fr iesian breed. The results demonstrate that the optimal concentration o f cytochalasin B to obtain the highest frequency of binucleated cells (mean = 400.26 +/- 23.76/1000 cells scored) was 6 mug/ml. The baseline frequency of spontaneous MN formation in 500 binucleated cells was 12 .3 +/- 4.1, i.e., 3 times higher than that reported in human lymphocyt es (Fenech and Morley, 1985; Scarfi et al., 1991). The possible reason (s) for this difference (sensitivity to cytochalasin B, chromosome num ber, environmental genotoxic pollutants) is discussed.