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Toxicological information

Genetic toxicity: in vivo

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Administrative data

Endpoint:
in vivo mammalian germ cell study: gene mutation
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: - short abstract on poster presentation
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1996

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
DNA was isolated from paraffin-embedded tumor sections (obtained from the forestomach of mice of the NTP bioassay on 1,2,3-trichloropropane, see chapter 7.7), amplified by polymerase chain reaction, and analyzed by direct sequencing for mutations in the ras-genes
GLP compliance:
no
Type of assay:
other: PCR analysis of nature of H-ras and K-ras mutations in tumors

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): 1,2,3-trichloropropane
- no further information given

Test animals

Species:
mouse
Strain:
B6C3F1
Sex:
male/female
Details on test animals and environmental conditions:
see chapter 7.7 "National Toxicology Program (1993) / Mouse"

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
- corn oil
- see chapter 7.7 "National Toxicology Program (1993) / Mouse"
Details on exposure:
see chapter 7.7 "National Toxicology Program (1993) / Mouse"
Duration of treatment / exposure:
2 years, see chapter 7.7 "National Toxicology Program (1993) / Mouse"
Frequency of treatment:
daily 5 d/wk
Post exposure period:
non
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 6, 20 and 60 mg/kg
Basis:
actual ingested
gavage
No. of animals per sex per dose:
60
Control animals:
yes, concurrent vehicle

Examinations

Tissues and cell types examined:
paraffin-embedded tumor sections from the forestomach
Details of tissue and slide preparation:
DNA was isolated from paraffin-embedded tumor sections (obtained from the forestomach of mice of the NTP bioassay on 1,2,3-trichloropropane, see chapter 7.7), amplified by polymerase chain reaction, and analyzed by direct sequencing for mutations in the ras-genes

Results and discussion

Additional information on results:
- 10 of 16 analysed tumors had a highly specific H-ras or K-ras mutation.
- 6 of the 10 had a H-ras mutation at codon 61 with 5 of the 6 showing a AT to TA transversion in base 1.
- 4 of the 10 had a K-ras mutation at codon 13 all of which showed a GC to CG transversion in base 1.
- These transversions aremost probably not caused by S-[1-(hydroxymethyl)-2-(N7- guanypethyl]glutathione which is the major DNA adduct that was found after 1,2,3-trichloropropane treatment.
- Based on preliminary results that are not further specified in the abstract, the authors propose that the found mutations are rather caused through etheno DNA adducts (1,N6-ethenodeoxyadenosine and 3,N4-ethenodeoxycytidine) which stem from lipid peroxidation.
- Their explanation is that the depletion of glutathion in cells that are exposed to 1,2,3-trichloropropane cause an increase in lipid peroxidation and thereby lead to the detrimental transversion mutations that were found in the ras-genes.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): positive
DNA was isolated from paraffin-embedded tumor sections (obtained from the forestomach of mice of the NTP bioassay on 1,2,3-trichloropropane, see chapter 7.7), amplified by polymerase chain reaction, and analyzed by direct sequencing for mutations in the ras-genes.
Based on these results it is confirmed that 1,2,3-trichloropropane induces mutations, but a alternative mode of action is proposed: 1,2,3-trichloropropane exposure leads to glutathion depletion in cells, lipid peroxidation increases and etheno DNA adducts are formed that lead to transversion mutations.
Executive summary:

The present abstract to a poster presentation (Ito, 1996) reports the analysis of mouse forestomach tumor tissues via PCR. DNA was isolated from paraffin-embedded tumor sections (obtained from the forestomach of mice of the NTP bioassay on 1,2,3-trichloropropane, see chapter 7.7), amplified by polymerase chain reaction, and analyzed by direct sequencing for mutations in the ras-genes.

10 of 16 analysed tumors had a highly specific H-ras or K-ras mutation. 6 of the 10 had a H-ras mutation at codon 61 with 5 of the 6 showing a AT to TA transversion in base 1. 4 of the 10 had a K-ras mutation at codon 13 all of which showed a GC to CG transversion in base 1. These transversions are most probably not caused by S-[1-(hydroxymethyl)-2-(N7- guanypethyl]glutathione which is the major DNA adduct that was found after 1,2,3-trichloropropane treatment.

Based on preliminary results that are not further specified in the abstract, the authors propose that the found mutations are rather caused through etheno DNA adducts (1,N6-ethenodeoxyadenosine and 3,N4-ethenodeoxycytidine) which stem from lipid peroxidation. The proposed explanation is that the depletion of glutathion in cells that are exposed to 1,2,3-trichloropropane causes an increase in lipid peroxidation and thereby lead to the detrimental transversion mutations that were found in the ras-genes.