Direct evidence for in vivo hydroxyl radical generation in blood of mice after acute chromium(VI) intake - Electron spin resonance spin-trapping investigation

Although it is assumed from in vitro experiments that the hydroxyl radical ( OH) may be responsible for chromium(VI) toxicity/ carcinogenicity, no ele ctron spin resonance (ESR) evidence for the gen eration of . OH in vivo has been reported. In this study, we have employed an ESR spin-trapping techni que with 5,5-dimethylpyrrolineN-oxide (DMPO), a selective OH trap, to detec t . OH in blood. The ESR spectrum of spin adduct observed in the blood of m ice given 4.8 mmol Cr(VI)/kg body weight exhibited the 1 : 2: 2: 1 intensit y pattern of a quartet with a hyperfine coupling constant A(N) = A(H) = 14. 81 G and g-value = 2.0067. The concentration of the spin adduct detected in the blood was 7.37 mu M The adduct production was inhibited by the additio n of specific OH scavengers such as sodium benzoate and methional to the bl ood. The results indicate that the spin adduct is nitroxide produced by the reaction of OH with DMPO. This is the first report of ESR evidence for the in vivo generation of OH in mammals by Cr(VI).