Immunohistochemically Detected O6- and N7-Methyldeoxyguanosine in Organs of Rats Administrated N-Methyl-N-Nitrosourea.

Abstract

The production of DNA adducts, O6-methyldeoxyguanosine (O6-medG) and N7-methyldeoxyguanosine (N7-medG), was examined in various organs of rats administrated N-methyl-N-nitrosourea (MNU) using an immunohistochemical approach. Fisher 344 rats divided into 4 groups were treated with alkylating agents. Animals in groups I and 2 were administered MNU (20mg/kg) intragastrically and intraperitoneally, respectively. Animals in group 3 were administered dimethylnitrosamine (DMN) (60mg/kg, i.p.) as a positive control and group 4 was maintained as a negative control group. At 10 hours after the carcinogen administration, rats were killed under ether anesthesia and the liver, stomach, and esophagus were removed from each. In the animals treated with MNU i.g., N7-medG positive nuclei were found in forestomach, glandular stomach, liver, and esophagus while only the liver and forestomach were positive after the i.p. treatment. O6-medG positive cells were not detected in any organs of animals receiving MNU (i.g. or i.p.). In the livers of animals treated with DMN, nuclei of hepatocytes were strongly stained with antibodies to both 06-and N7-modG. In the control group no O6-or N7-medG positive cells were detected in any of the organs.