title: Viscometric analysis of DNA damage in kidney and lung following exposure of rats to small doses of chemical carcinogens.
abstract: A new viscometric technique has been used to detect DNA damage in kidney and lung of rats treated with six chemical carcinogens. In alkaline conditions (pH 12.5) the reduced viscosity (eta red) of kidney and lung DNA from control rats increased slowly with time reaching a maximum, (eta red)max, after 9-12 h. Carcinogens, by inducing DNA strand breaks either chemically or indirectly by excision repair or during incubation in alkali, cause a reduction of DNA supercoiling which can be sensitively measured by monitoring changes in viscosity. Computerized analysis of time-viscosity curves showed that a statistically significant reduction of the time required for eta red to reach 95% of its maximum value (t-95) was induced by the following single i.p. doses: N-nitrosodimethylamine (DMN), kidney 0.07 mg/kg, lung 0.28 mg/kg; N-nitrosodiethylamine (DEN), kidney 3.2 mg/kg, lung 12.8 mg/kg; N-nitroso-N-methylurea, kidney and lung 0.5 mg/kg; 1,2-dimethylhydrazine (DMH), kidney 1 mg/kg, lung 16 mg/kg; 4-nitroquinoline-1-oxide (NQO), kidney 2.5 mg/kg, lung 0.63 mg/kg; 2-acetylaminofluorene, kidney and lung 12.5 mg/kg. The decrease of t-95 was constantly dose-related. The comparison with data previously obtained from liver demonstrates that DMN, DEN, DMH and NQO caused the greatest amount of DNA damage in the organ most susceptible to tumor induction. Viscosity changes elicited by DMN, DEN and DMH are quantitatively well correlated with the extent of DNA alkylation.
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000633:toxicity*; D004247:DNA / Q000378:metabolism*; D007668:Kidney / Q000187:drug effects / Q000473:pathology*; D008168:Lung / Q000187:drug effects / Q000473:pathology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014783:Viscosity
chemical_list: D002273:Carcinogens; D004247:DNA