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Toxicological information

Genetic toxicity: in vivo

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Administrative data

Endpoint:
in vivo mammalian cell study: DNA damage and/or repair
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
Dose-response curves for liver DNA fragmentation induced in rats by sixteen N-nitroso compounds as measured by viscometric and alkaline elution analyses
Author:
Brambilla G, Carlo P, Finollo R, Sciaba L.
Year:
1987
Bibliographic source:
Cancer Research 47, 3485-3491, July 1

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
A new viscometric technique, capable of detecting DNA strand breaks and alkali-labile sites by monitoring time-dependent changes of DNA-reduced viscosity, has been used to analyse dose-response curves for the induction of DNA damage in liver of rats treated with single p.o. doses.
The contemporary measurement of liver DNA fragmentation by the alkaline elution technique revealed hat in the experimental conditions higher doses are needed to produce statistically significant increase of DNA elution rate. This suggests that the viscometric method is capable of detecting smaller levels of N-nitroso compound induced DNA fragmentation.
GLP compliance:
no
Type of assay:
other: DNA fragmentation

Test material

Constituent 1
Chemical structure
Reference substance name:
Nitrosodiphenylamine
EC Number:
201-663-0
EC Name:
Nitrosodiphenylamine
Cas Number:
86-30-6
Molecular formula:
C12H10N2O
IUPAC Name:
N-nitroso-N-phenylaniline
Specific details on test material used for the study:
Abbreviation in the publication : NDPHA
molecular weight : 198.2 g/mol

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male
Details on test animals or test system and environmental conditions:
- Weight at study initiation: 160-180g
- Assigned to test groups randomly: yes
- Fasting period before study: 12h

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
Nitrosodiphenylamine was suspended in distilled water with 1% carboxymethyl cellulose
Details on exposure:
A single dose was administered by gavage in 0.01 ml of vehicle/g of body weight.
Duration of treatment / exposure:
only one treatment
Frequency of treatment:
only one treatment
Post exposure period:
Rats were sacrified 3h after treatment.
Doses / concentrations
Dose / conc.:
540 mg/kg bw/day
Remarks:
corresponding of one-third of LD50
No. of animals per sex per dose:
Control groups : 20 rats
Treated groups : 3 rats
Control animals:
yes, concurrent vehicle
Positive control(s):
no

Examinations

Tissues and cell types examined:
Liver cells
Details of tissue and slide preparation:
Liver cell nuclei of treated and control rats were obtained by liver perfusion, and analyzed viscometrically in alkaline conditions (pH 12.5) at high ionic strength (I = 1.08). The cells harvested with the procedure used were predominantly of the lobular prenchyma. The number of nuclei lysed in the circular channel of the viscometer ranged from 6 to 7 x 10^7.
Results are expressed as reduced viscosity that is the viscosity of DNA solution for conentration units of DNA, determined at the end of each experiment.
To obtain quantitative parameters, viscosity measurements were performed at 20 and 40-min intervals.

Results and discussion

Test results
Sex:
male
Genotoxicity:
negative
Toxicity:
no effects
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
not examined
Additional information on results:
Fragmentation of rat liver DNA :
DNA damage was absent in the liver of rats given 540 mg/kg of nitrodiphenylamine.
% DNA eluted from the filter : 19.2 +/-6.3
DNA elutation rate over controls : 0.0020

Effet of nitrosodiphenylamine on viscometric behavior of rat liver DNA :
The time required for DNA reduced viscosity to reach 95% = T95 = 1411 min +/-88 min
Reduced viscosity at 95% = 3.05 +/-0.11 (x10-2 dl/g)
Slope = 0.22 +/- 0.03 x 10-2

Applicant's summary and conclusion

Conclusions:
DNA damage was undetectable in liver of rats treated with 540 mg/kg of nitrosodiphenylamine, that exhibited a plateau effect.
Executive summary:

A new viscometric technique, capable of detecting DNA strand breaks and alkali-labile sites by monitoring time-dependent changes of DNA-reduced viscosity, has been used to analyse dose-response curves for the induction of DNA damage in liver of rats treated with single p.o. doses.

The contemporary measurement of liver DNA fragmentation by the alkaline elution technique revealed hat in the experimental conditions higher doses are needed to produce statistically significant increase of DNA elution rate. This suggests that the viscometric method is capable of detecting smaller levels of N-nitroso compound induced DNA fragmentation.

With both techniques, DNA damage was undetectable in liver of rats treated with 540 mg/kg of nitrosodiphenylamine, that exhibited a plateau effect.