Comparison of baseline Sister-Chromatid Exchanges (SCE), cyclophosphamide-, ethylnitrosourea (ENU)-induced SCE, ENU-induced cell-cycle delay and chromosome aberrations between Peru and laboratory mice

Abstract

The baseline sister-chromatide exchange (SCE) frequency and sensitivity to the effects of the mutagens cyclophosphamide (CPP) and ethylnitrosourea (ENU) in bone-marrow cells descedants of wild mice trapped from Rimac valley in Peru (Peru mice) were studied and compared to the same effects in laboratory mice. Baseline SCE of the Peru mice were significantlyhigher than those of the C57BL/6J and DBA/2 mice. The average SCE/cell of 4 Peru mice was 5.4 (range 3.8–7.6), while the average of SCE/cell of either 4 C57BL or 5 DBA mice was 3.2 (range 3.0–3.4). The variation of SCE/cell among Peru mice studied was statistically significant whereas among C57BL or DBAmice it was not. SCE frequencies of primary cultures derived from the ear tissue of 10 peru (mean SCE/cell = 8.5) were also significantly higher than those of 6 C57BL mice (mean SCE/cell = 7.4). CPP treatment resulted in a dose-dependent increase of SCE frequencies in bone-marrow cells of all the mice. However, some Peru mice treated with CPP had significantly higher SCE than the other Peru mice and than all of the C57BL and DBA mice treated with equivalent dose. ENU induced increased SCE frequencies in EPru and C57BL mice. Again some of peru mice either had significantly higher SCE, greater induced cell-cycle delay or chromosome aberrations (CA) than other Peru mice and than of all the C57BL mice treated with equivalent dose. These data suggest that there are two classes of Peru mice, one with high baseline SCE, which is possibly sensitive to the mutagenic effects, as measured by induction of SCE, cell cycle delay and CA; and one class with low baseline SCE which behaves the same as the laboratory mice.