DNA damage induced by carcinogenic lead chromate particles in cultured mammalian cells.
Particulate lead chromate is a highly water-insoluble cytotoxic and carcinogenic agent, but its mechanism of action remains obscure. We investigated its effects on DNA damage in CHO cells after a 24-h exposure using alkaline or neutral filter elution and cytogenetic studies. Concentrations (0.08, 0.4 and 0.8 micrograms/cm2), which reduced the colony-forming efficiency of CHO cells to 94, 50 and 10%, respectively, produced dose-dependent DNA single-strand breaks and DNA-protein crosslinks, but no DNA double-strand breaks or DNA-DNA crosslinks were observed. The single-strand breaks were absent from cells given a 24-h recovery period after removal of the treatment medium, even though most of the particles remained adhered to cells and to the culture dish. In contrast, both the DNA-protein crosslinks and chromosomal aberrations persisted even after the 24-h recovery period. These results suggest that the mechanism of the particle-induced early DNA single-strand breaks may be different from DNA-protein crosslinks and the lesions leading to chromosomal aberrations, or alternatively, that the repair of single-strand breaks is more efficient than the repair of DNA-protein crosslinks in the unavoidable continuing presence of carcinogen. These results also suggest that the chromosome damage may be related to the persistent DNA-protein crosslinks, and further confirm the genotoxic activity of carcinogenic lead chromate particles.
Xu
J
J
Department of Pharmacology, George Washington University Medical Center, Washington, DC 20037.
Wise
J P
JP
Patierno
S R
SR
D000818:Animals; D016466:CHO Cells; D002273:Carcinogens / Q000633:toxicity*; D002478:Cells, Cultured; D002840:Chromates / Q000633:toxicity*; D002869:Chromosome Aberrations; D006224:Cricetinae; D004249:DNA Damage; D007854:Lead / Q000633:toxicity*
D002273:Carcinogens; D002840:Chromates; D007854:Lead; C031895:lead chromate