Effects of ethanol on the DNA-damage induced by 2 carcinogenic nitrosamines

We studied the DNA single-strand breaks (DNA SSBs) induced by two nitrosamines using rat hepatocytelin situ nick translation assay. In the hepatocytes treated with 20 mu M of N-nitrosodimethylamine (NDMA), 100 mM ethanol enhanced DNA SSBs 3 times higher than those of control. However, there was no significant difference between the DNA SSBs with and without ethanol in 300 mu M of N-nitrosodiethylamine (NDEA) treated groups. Pretreatment of 100 mM ethanol increased P450IIE1 levels determined by Western blotting, whereas the amount of total P450 was not affected. Although NDMA is possibly activated by P450IIE1, there could be other isozymes responsible for the activation of NDEA. Phenobarbital inducible isozymes such as P450IIB1 and IIB2, or P450IIA3 may be primarily responsible.