Is 8-hydroxydeoxyguanosine a mediator of carcinogenesis by a choline-devoid diet in the rat liver?

The mechanism(s) by which a diet devoid of choline (CD) induces hepatocellular carcinomas in rats remains unknown. Although animals fed this diet develop nuclear lipid peroxidation, suggesting oxidative DNA damage, there is no direct evidence that this occurs. In this study, 8-hydroxydeoxyguanosine (8-OHdG), a DNA adduct generated by reactive oxygen species, was analyzed in the liver of rats fed a CD diet and in controls receiving a choline-sufficient (CS) diet. After partial hepatectomy, the animals were injected with diethylnitrosamine (DEN, 50 mg/kg body wt) or with saline and fed a CD or CS diet for 24 weeks. While liver DNA from rats injected either with DEN or saline and fed a CS diet did not show detectable amounts of the nucleotide, those who were fed DEN/CD and saline/CD demonstrated similar, easily measurable levels of 8-OHdG. These results indicate that there is a positive association between the continuous administration of a CD diet and the production of 8-OHdG in liver DNA, and support the idea that oxidative DNA damage is involved in carcinogenesis by a CD diet.