SPONTANEOUS RATE OF SISTER-CHROMATID EXCHANGES (SCES) AND BRDU DOSE-RESPONSE RELATIONSHIPS IN MITOTIC CHROMOSOMES OF GOAT (CAPRA-HIRCUS L)

The spontaneous level of sister chromatid exchange (SCEs) in the goat, estimated by exposing peripheral blood lymphocytes to 0.1 mu g/ml of 5-bromodeoxyuridine (BrdU), was 3.28 +/- 1.71 SCE/cell, 1.64 SCE/cell generation and 0.027 SCE/chromosome. The dose-response curve of SCE/ce ll, observed by exposing the cells to 0.1, 0.25, 0.5, 1.0, 2.5, and 5. 0 mu g/ml of BrdU, rose rapidly From 0.1 to 0.5 mu g/ml, remained fair ly stable from 0.5 to 1.0 mu g/ml and rose less rapidly from 1.0 to 5. 0 mu g/ml of BrdU. The frequency distribution of sister chromatid exch anges/cell and that of chromosomes showing various number of exchanges followed the Poisson probability at all BrdU levels; only at 5.0 mu g /ml of BrdU was the fit found on the border of the 5 % probability lev el. The usefulness of determining the spontaneous level of SCE/cell in domestic animals is discussed in relation to its possible application for a more precise evaluation of the genotoxic effects of environment al pollutants.