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Toxicological information

Genetic toxicity: in vivo

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Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Remarks:
Type of genotoxicity: DNA damage and/or repair
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1992
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: 1a GLP Guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1992

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
GLP compliance:
yes
Type of assay:
micronucleus assay

Test material

Constituent 1
Chemical structure
Reference substance name:
Pentafluoroethane
EC Number:
206-557-8
EC Name:
Pentafluoroethane
Cas Number:
354-33-6
Molecular formula:
C2HF5
IUPAC Name:
1,1,1,2,2-pentafluoroethane
Details on test material:
- Name of test material (as cited in study report): HCFC-125
- Physical state: Gasseous
- Analytical purity: >99%
- Impurities (identity and concentrations): not reported
- Lot/batch No.: UN1956

Test animals

Species:
mouse
Strain:
CD-1
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories UK
- Age at study initiation: 4-5 weeks
- Weight at study initiation: 20-30 g
- Assigned to test groups randomly: yes
- Fasting period before study:
- Housing: Mice housed in polypropylene/stainless steel cages (groups 3-5 animals of the same sex)
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: 4-6 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 +/-3 °C
- Humidity (%): 50+/- 10%

Administration / exposure

Route of administration:
inhalation
Details on exposure:
TYPE OF INHALATION EXPOSURE: nose only

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Exposure chamber (aluminium alloy cylinder of 30 cm diameter, 60 liter volume) with restraing tubes
- Method of holding animals in test chamber: mice were kept in the restraining tube with the snout protruded to the exposure chamber during the exposure period
- Source and rate of air: COmpressed air filtrated and mixed with the test substance (+ oxygen fo the 12 and 60% target concentration, in order to mantain the O2 concentration in the range 19-21%:
- Air flow rate: 0.25 l/min

TEST ATMOSPHERE
- Brief description of analytical method used: GC analysis with thermal conductivity detector performed at hourly intervals during the exposure period
- Samples taken from breathing zone: yes
Duration of treatment / exposure:
6 hrs
Frequency of treatment:
Single
Post exposure period:
24, 48 and 72 hours
Doses / concentrations
Remarks:
Doses / Concentrations:
2.4%, 12% and 60% v/v in atmosphere
Basis:
nominal conc.
No. of animals per sex per dose:
5
Control animals:
yes, concurrent no treatment
Positive control(s):
Chlorambucil 30 mg/kg (oral administration)

Examinations

Tissues and cell types examined:
Bone marrow erythrocytes
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION:
Prelinminary toxicity test carried out at the maximalm dose used in the main test

TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields):
5 mice/sex/group were exposed to 0, 2.4, 12 and 60% (v/v) for 6 hours and sacrified on 24 hours after the start of the exposure. Further 5 mice/sex/group were exposed to 0 and 60% HFC-125 for 6 hours and sacrified on 48 and 72 hours after the start of the exposure.

DETAILS OF SLIDE PREPARATION:
Bone marrow smears on glass slides were made and stained from each animal.

METHOD OF ANALYSIS:
Visula examination perfomed by light microscope. At least 2000 erythrocytes per animal were examined for the presence of micronuclei

Evaluation criteria:
number of micronucleated cells per 1000 polychromatic erythrocytes was determined for all animals exposed to HFC-125 and compared with the incidence in negative controls. THe ratio polychromatic/mature erythrocytes was calculated to assess the cytotoxic effects.
Statistics:
Mann-Whitney U test was used for the statistical analysis of the micronucleus incidence

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
RESULTS OF RANGE-FINDING STUDY

- Clinical signs of toxicity in test animals: Clinical signs of toxicity (hunched posture, tremors, hypoactivity and slow respiration) were observed in animals exposed to 60% HFC-125
- Evidence of cytotoxicity in tissue analyzed: No changes were observed in the polychromatic/mature erythrocytes ratio among the animals treated with HFC-125 and the negative controls


RESULTS OF DEFINITIVE STUDY
- Induction of micronuclei (for Micronucleus assay): No statistically significant changes in the frequency of micronucleated polychromatic erythrocytes were observed among the groups treated with HFC-125 and the negative control group
- Ratio of PCE/NCE (for Micronucleus assay): No changes were observed among the group treated with HFC-125 and the negative control group

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
HFC- was not genotoxic under the test conditions
Executive summary:

Groups of male and female mice were exposed to 2.4, 12 and 60% v/v HFC 125 in the atmosphere. 5 male and 5 female mice per group were killed 24 hrs, 48 hrs  and 72 hrs after the exposure.
A preliminary toxicity test was carried out.
Concurrent negative and positive control groups were exposed to air or administered 30 mg/kg chlorambucil, respectively.
Bone marrow smears on glass slides were made from each animal.
A total of at least 2000 erythrocytes/animal was examined for the presence of micronuclei. Calculated number of micronuclei per 1000 polychromatic erythrocytes were analysed. The ratio of polychromated/mature cells was also determined as an indicator of cytotoxicity.

Statistical analysis:
The frequency of micronucleated cells were analysed by means of the Mann-Withney U test.

Result:
mice exposed to HFC-125 60% showed clinical signs of toxicity (hunched posture, tremors, hypoactivity). All mice killed 24 hrs after the exposure had lost weight.

No statistically significant increased frequency of micronucleated erythrocytes was observed in any group treated with HFC 125 in comparison to negative control.
Chlorambucil treatment significantly increased the number of micronucleated cells in comparison to control (p0.01).

No significant changes were observed in the ratio polychromated/mature cells, among the control groups, the groups treated with HFC 125 and the chlorambucil-treated groups.

Conclusion:
Under the conditions of test, HFC 125 did not induce any chromosomal damage or other clastogenic effect leading to micronuclei formation in polychromatic murine erythrocytes.