Chromosomal aberrations and sister-chromatid exchanges in Chinese hamster cells treated in vitro with hexavalent chromium compounds

Abstract

Chinese hamster cells (CHO line) were treated in vitro for 30–39 h with hexavalent chromium compounds (K 2Cr 2O 7 and Na 2Cr 2O 7), at concentrations ranging from 0.1 to 1.0 μg of Cr 6+ per ml, in medium containing BUdr. Chromosomal aberrations and sister-chromatid exchanges were scored on BUdr-labelled 2nd division metaphases, collected at the end of treatment and stained with Giemsa. Treatment with mitomycin C (0.009–0.030 μg/ml) was carried out as a control for the responsiveness of the cell system to chromosomal damage. Both chromium compounds induced marked mitotic delays. Chromosomal aberrations were increased about 10-fold by exposure to Cr 6+ (1.0 μg/ml). The principal aberrations observed were single chromatid gaps, breaks and interchanges, whose frequencies increased proportionally to the concentration of chromium. Dicentric chromosomes, isochromatid breaks, chromosome and chromatid rings were also induced. The frequency of sister-chromatid exchanges was hardly doubled 30 h after exposure to Cr 6+ at 0.3 μg/ml, whereas it was trebled 39 h after treatment, in the cells whose division cycle had been slowed down by chromium.