Lipid peroxidation induced by N-nitrosodimethylamine (NDMA) in rats in vivo and in isolated hepatocytes.

To investigate the role of carcinogenic chemicals as a possible cause for oxidative damage, rats were treated with N-nitrosodimethylamine (NDMA) and various measures of lipid peroxidation were followed. As an indication of enhanced peroxidative processes in vivo, NMDA treatment produced rapidly an increase in the rate of ethane exhalation. A single i.p. or p.o. injection of 10 mg/kg b.w. elevated ethane exhalation by 13-14 fold; a single dose of 0.5 mg/kg of NDMA (the smallest dose tested) increased 5-fold the amount of ethane exhaled. Similarly, lipid peroxidation in the liver of NDMA-treated rats (measured by diene conjugation, chemiluminescence, the production of fluorescent and TBA-reactive material) was found to be increased rapidly showing a peak already 20 min after dosing. Simultaneously, NDMA-treatment slightly decreased antioxidant enzyme activities and GSH contents in the liver. In isolated rat hepatocytes the lucigenin-dependent chemiluminescence, as well as H2O2 release, were increased by micromolar concentrations of NDMA. Finally, it was shown that the rate of NADPH-stimulated ethane production by hepatic microsomes, prepared from untreated rats, was increased in the presence of NDMA. Thus, our results demonstrate that the alkylating NDMA can induce oxidative stress in rodents. Whether the same is true for other classes of carcinogens and processes known to affect tumor initiation/progression is presently under investigation.