FORMATION AND PERSISTENCE OF THE MISCODING DNA ALKYLATION PRODUCT O-6-ETHYLGUANINE IN MALE GERM-CELLS OF THE HAMSTER

The cellular parameters which modulate trans germ-line carcinogenesis by DNA-reactive agents have not yet been studied in detail. Therefore, we have measured in this study the formation and repair kinetics of t he miscoding alkylation product O-6-ethylguanine (O-6-EtGua) in nuclea r DNA of spermatogonial cells of the Syrian golden hamster (SGH) after exposure to either of two potent N-nitroso carcinogens, ethylnitrosou rea (ENU) or diethylnitrosamine (DEN). Both compounds, the spontaneous ly decomposing ENU, and DEN, which has to be converted by cellular enz ymes to the reactive ethyl diazonium ion, induce the same pattern of a lkylation products in nuclear DNA. Adduct analyses were performed at t he single-cell level by using a quantitative immunocytological assay a nd anti-(O-6-EtGua) monoclonal antibodies. 1.5 h after intraperitoneal application of ENU (100 mu g/g body weight) O-6-EtGua levels in the n uclear DNA of spermatogonia were similar to those in other cell types of the same hamster. About 30% of the initially formed DNA adducts wer e still persistent in spermatogonial cells even 4 days after ENU expos ure, The presence of O-6-EtGua in DNA after exposure to DEN (100 mu g/ g body weight) implies the capability of hamster spermatogonial cells to convert nitrosamines into DNA-alkylating metabolites, This capabili ty of male germ cells in combination with their limited repair capacit y for a critical DNA adduct and their high rate of proliferation may b e considered as a major risk factor for genetic effects including carc inogenesis in subsequent generation(s). (C) 1997 Elsevier Science B.V.