Induction of 8-hydroxy-2'-deoxyguanosine by cobalt(II) and hydrogen peroxide in vitro.

In order to test the effects of cobalt on oxidative DNA damage, we measured the formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the presence of cobalt in calf thymus DNA and in DNA of human diploid fibroblasts. Treatment of calf thymus DNA with Co(II) at 500 µ M hydrogen peroxide resulted in a dose-dependent increase in 8-OHdG, which culminated at 25 µ M Co(II) (62.6 modified/105 dG) and declined at higher Co(II) concentrations [9.6 modified/10 5 dG at 250 µ M Co(II)]. Incubation of calf thymus DNA with Co(II) alone did not cause an increase in 8-OHdG. Treatment of calf thymus DNA with H 2 O 2 (0.25-2 m M ) caused only a slight generation of 8-OHdG (2.7/10 5 dG, at 2 m M H 2 O 2 ). Exposure of human diploid fibroblasts to Co(II) at 5-250 µ M did not result in an increase in 8-OHdG in a dose-dependent manner, although treated cells showed significantly higher 8-OHdG levels than untreated controls (2.026 - 0.695 vs. 1.395 - 0.433 8-OHdG/10 5 dG) at all concentrations. Our data indicate that in the pres...