Formation and persistence of O6-(2-hydroxyethyl)-2' -deoxyguanosine in DNA of various rat tissues following a single dose of N-nitroso-N-(2-hydroxyethyl)urea. An immuno-slot-blot study.
Rabbit antibodies against O6-(2-hydroxyethyl)-2'-deoxyguanosine (O6-HEdg) were used to develop a highly sensitive immuno-slot-blot assay for this promutagenic base which enabled the quantitation of greater than or equal to 3.6 mumol O6-HEdG/mol deoxyguanosine, corresponding to greater than or equal to 5 fmol in a 3-mug DNA sample. This assay was used to study DNA hydroxyethylation by N-nitroso-N-(2-hydroxyethyl)urea (HENU) in adult male F344 rats. Initial amounts of O6-HEdG 2 h after a single i.v. dose of 50 mg/kg were highest in kidney (81 mumol O6-HEdG/mol deoxyguanosine), followed by lung and liver (67 and 55 mumol/mol dG respectively). Formation of O6-HEdG in cerebral DNA was considerably lower (18 mumol O6-HEdG/mol deoxyguanosine), probably reflecting delayed crossing of the blood-brain barrier by HENU due to its hydrophilicity. The formation of O6-HEdG in liver and kidney was strictly proportional to dose over a range of 5-50 mg HENU/kg. Repair of O6-HEdG was very rapid in liver (apparent half-life, 12 h), and somewhat slower in kidney and lung (approximate half-life, 40 h and 48 h respectively). In contrast, 62% of the initial amount of O6-HEdG in cerebral DNA was still present after 7 days. Saturation of the hepatic O6-alkyl-guanine-DNA alkyltransferase by pretreatment with N-nitroso-dimethylamine (20 mg/kg) almost completely inhibited the removal of O6-HEdG, indicating that O6-HEdG is predominantly repaired by this repair enzyme.
Ludeke
B I
BI
Laboratory of Neuropathology, University of Zurich, Switzerland.
Kleihues
P
P
D000818:Animals; D004247:DNA / Q000378:metabolism*; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005038:Ethylnitrosourea / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D007163:Immunosorbent Techniques; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D014018:Tissue Distribution
C054529:O(6)-(2-hydroxyethyl)-2'-deoxyguanosine; C022146:1-(2-hydroxyethyl)-1-nitrosourea; D004247:DNA; D003849:Deoxyguanosine; D005038:Ethylnitrosourea