Genetic effects of chromium compounds.

Seven different test systems were utilized to investigate the genetic activity of chromium compounds: infidelity of DNA replication in vitro by DNA pol alpha from calf thymus, damage of DNA detected by alkaline elution in treated mammalian cells or in DNA purified and treated in vitro, DNA repair synthesis in mammalian cells in vitro detected by autoradiography or scintillation counting after labelling with [3H]dThd, gene mutations in the Salmonella typhimurium Ames test, gene mutations (6TG resistance) in cultured hamster cells, sister-chromatid exchanges in different rodent cell cultures, and transformation to anchorage-independent growth of hamster cells in vitro (soft-agar assay). Potassium dichromate and chromium chloride were used as water-soluble Cr(VI) and Cr(III) salts. Several reference mutagens (EMS, MMS, MMC, 4NQO) were included in the single tests as positive controls. Cr(VI) was active in all the tested systems, except in the induction of DNA damage and DNA repair synthesis in cultured cells. Cr(III), on the other hand, was absolutely inactive unless a direct interaction with purified DNA was permitted by the test conditions. The relevance of data from the various tests to the understanding of the mechanisms of the genotoxic activity of chromium is discussed. Effects other than the direct interaction of Cr(III) with DNA are inferred, which can cause infidelity of the DNA polymerase functions.