Cytotoxic and genotoxic effects of paraquat in Hordeum vulgare and human lymphocytes in vitro

Two phylogenetically distant types of test‐systems—root tip meristems of barley (Hordeum vulgare) and human lymphocytes in vitro were used to detect genotoxicity and cytotoxicity induced by the herbicide paraquat (PQ) in the concentration range (10^?6 to 5 × 10^?4 mol/l). As an endpoint for cytotoxicity the mitotic index (MI) was evaluated. The frequency of chromosome aberrations (CA) and the frequency of micronuclei (MN) were used as endpoints for genotoxicity. A dose‐dependent increase of CA and MN was observed in both test systems, although the values for PQ‐induced MN were somewhat lower. The increase of the genotoxic effect corresponds to a decrease of mitotic activity. The structurally reconstructed barley karyotype MK14/2034 allowed the allocation of the PQ‐specific features of aberration distribution patterns and gave information about which chromosome segments in different chromosomal positions were involved in induced aberrations. Paraquat produced preferably isochromatid breaks and “aberration hot spots” in a restricted number of heterochromatin‐containing segments. The comparative analysis of susceptibility in the used test‐systems to PQ with respect to its cytotoxic and clastogenic effect showed that the human lymphocytes were more sensitive than Hordeum vulgare. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.