Chromosome aberration and sister chromatid exchange test results with 42 chemicals

Forty-two chemicals were tested for their ability to induce cytogenetic change in Chinese hamster ovary cells using assays for chromosome aberrations (ABS) and sister chromatid exchanges (SCE). These chemicals were included in the National Toxicology Program's evaluation of the ability of four in vitro short-term genetic toxicity assays to distinguish between rodent carcinogens and noncarcinogens. The conclusions of this comparison are presented in Zeiger et al. [Zeiger E, Haseman JK, Shelby MD, Margolin BH, Tennant RW (1990): [Environ Molec Mutagen 16(Suppl 18): 1-14]. The in vitro cytogenetic testing was conducted at four laboratories, each using a standard protocol to evaluate coded chemicals with and without exogenous metabolic activation. Most chemicals were tested in a single laboratory; however, two chemicals, tribromomethane and p-chloroaniline, were tested at two laboratories as part of an interlaboratory comparison. Four chemicals (C.I. basic red 9 HCl, 2-mercaptobenzothiazole, oxytetracycline HCl, and rotenone) were tested for SCE in one laboratory and in a different laboratory for ABS. Tetrakis(hydroxymethyl)phosphonium sulfate was tested at one laboratory and the chloride form was tested at a different laboratory. Twenty-five of the 42 chemicals tested induced SCE. Sixteen of these also induced ABS; all chemicals that induced ABS also induced SCE. There was approximately 79% reproducibility of results in repeat tests, thus, we conclude that this protocol is effective and reproducible in detecting ABS and SCE.