Dissociation of the accumulation of single-strand breaks in DNA from the killing of cultured hepatocytes by an oxidative stress.

The relationship was explored between the accumulation of single-strand breaks in DNA and the killing of cultured hepatocytes by an oxidative stress generated by either tert-butyl hydroperoxide (TBHP), glucose oxidase, or menadione. The accumulation of DNA strand breaks was measured fluorometrically by the rate of the alkaline unwinding of DNA. In each case, DNA strand breaks were detected before the loss of cell viability. DNA damage and cell killing depended on a cellular source of iron. Pretreatment of the hepatocytes with the ferric iron chelator deferoxamine prevented both, and the readdition of iron to the medium restored the DNA damage and the cell killing. In addition, the radical scavenger keto-methiolbutyric acid reduced the extent of DNA damage and prevented the cell killing. By contrast, the antioxidants N,N'-diphenyl-p-phenylenediamine and butylated hydroxytoluene prevented the cell killing but not the DNA single-strand breaks induced by TBHP. Similarly, acidification of the culture medium also prevented the cell killing, without any effect on the extent of the DNA damage by TBHP, glucose oxidase, and menadione. These data indicate that DNA damage and cell killing produced by an oxidative stress depend upon the iron-catalyzed formation of a potent oxidizing species. However, the accumulation of such damage can be dissociated from the mechanisms that lethally injure the cells.