Cytogenetic Effects in Cultures of Human Lymphocytes Exposed to the Herbicide Paraquat

We conducted the experiments of the short-term (1 hour) testing effect of the herbicide paraquat, one of the strongest inducer of oxidative stress, on cultured blood cells (late G1 stage of the first mitosis, 4 × 10^–8 mol/l) of 9 healthy donors. In 60-hour (short-term) and 120-hour (long-term) lymphocyte cultures exposed to paraquat in vitro, the average frequencies of aberrant cells were 4.05 ± 0.55 and 9.42 ± 1.23%, respectively, which significantly exceeds the corresponding control levels: 1.16 ± 0.30 and 1.70 ± 0.50% (p = 0.008 and p = 0.018, respectively). The observed genotoxic effects are primarily due to the induction of simple chromatid aberrations (single fragments), the levels of which were 3.32 ± 0.40 and 8.92 ± 1.40 per 100 cells as a result of short-term and long-term lymphocyte cultivation, respectively (in comparison with 1.03 ± 0.34 and 1.56 ± 0.38 per 100 cells in the corresponding control). The frequencies of paired chromosomal fragments in cell cultures of both types also significantly (or on the trend level) exceeded the control frequencies (p = 0.046 and p = 0.068 for 60- and 120-hour cultures, respectively). No differences were found between 60- and 120-hour unexposed cell cultures in the level of aberrant cells and chromosome aberrations of all types. In contrast, long-term lymphocyte cultures exposed to paraquat demonstrated significantly increased levels of aberrant metaphases and single chromatid fragments compared to short-term exposed cultures (p = 0.001). Long-term effects were shown to be characterized by higher individual values of Cohen's omega (w) – from 0.157 to 0.259, compared to those for 60-hour cultures – 0.057 to 0.153. The obtained data indicate the induction of genomic instability in distant descendants of human lymphocytes exposed to short-term paraquat at the beginning of cultivation, and its individual nature.