Immunocytochemical studies on the formation and repair of O6-alkylguanine in rat tissues.

The immunocytochemical visualization of the carcinogen-DNA adducts O6-ethylguanine (O6-etGua) and O6-methylguanine (O6-meGua) in histological sections of a large series of rat tissues, including liver, pancreas, testis and oesophagus, is described. In the liver of rats treated with N-ethyl-N-nitrosourea (ENU), N-nitrosodiethylamine (NDEA) or N-nitrosodimethylamine (NDMA), large differences were found in the formation and/or repair of O6-alkylGua between different cell types, between hepatocytes of different localization, and also between normal and precancerous hepatocytes. Heterogeneity of O6-etGua formation and repair was also found in pancreatic tissue of rats treated with ENU. O6-etGua was relatively persistent in nonparenchymal liver cells, pancreatic islet cells, spermatogonia, renal glomeruli and smooth-muscle cells. Our aim is to extend the immunocytochemical analysis to other DNA adducts, and ultimately to human tissues.