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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: chromosome aberration
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study was done according to OECD 474 with no listed deviations, and the test substance is adequately defined

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001

Materials and methods

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

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Clear liquid
99.61% pure
Batch Number: H931363-A
Supplier: DuPont

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male/female
Details on test animals and environmental conditions:
Male and female animals weighed between 152.1-173.6 grams and 125.7 and 148.6 grams, respectively. Animals were randomly assigned to groups with sexes separated. Groups, n=5/sex/exposure group, were kept in cages with a controlled environment. The temperature was kept at 21°C with a relative humidity of 50%. The room was illumiated for 12 hours per day. Animals were provided food and tap water ad libitum except when it was witheld prior to exposure. Aniamls were acclimatized to at least 12 days prior to study initiation.

Administration / exposure

Route of administration:
inhalation: aerosol
Vehicle:
None
Details on exposure:
Liquid test material was delivered to a concentric jet atomiser and generated as droplets into a stream of dry air for administraion to the rats in whole body exposure chambers. Exposure concentration was achieved by meteringthe test substance from polypropylene syringes mounted on syringe drivers.

Exposures were:
0 mg/L (Air) - Negative control
0.5 mg/L (0.545 analytical)
1.0 mg/L (0.807 anayltical)
2.0 mg/L (2.298 analytical)
20 mg/kg Cyclophosphamide (positive control)
Duration of treatment / exposure:
6 hours/day
Frequency of treatment:
2 days
Post exposure period:
24 hours
Doses / concentrations
Remarks:
Doses / Concentrations:

Basis:
analytical conc.
No. of animals per sex per dose:
5/sex/dose
Control animals:
yes
Positive control(s):
Cyclophosphamide 20 mg/kg adminstered by oral gavage at the end of the second exposure treatment

Examinations

Tissues and cell types examined:
Femoral bone marrow
Details of tissue and slide preparation:
Following sacrifice of animals, Both femurs of each animal were removed and bone marrow extracted and pooled into 10 mL of salt solution. The cell suspensions were centrifuged at 1000g for 5 minutes. The pellet was resuspended in 2 ml of filtered fetal calf serum to facilitate smearing on glass slides. Several smears were prepared from each femur. A modified Feulgen staining method was used which stains DNA-containing bodies deep purple without staining mast cell granules. The method also allows for differentiation of mature and immature erythrocytes.
Evaluation criteria:
Slides were examined by light microscopy to determine the incidence of micronucleated cells per 2000 polychromatic erythrocytes. Micronuclei were identified with the following criteria:
- large enough to discern morphological characteristics
-should be generally rounded in shape with clearly defined outline
-should be deeply stained and in color similar to other nuclei
-should lie in the same focal plane as the cell
-lack internal structure
-there should be no micronulceus like debris surrounding the cell

A portion of immature erythrocytes for each animal was asessed by examination of at least 1000 erythrocytes.

A positive repsonse is normally indicated by a statistically significant dose-related increase in the incidence of micronucleated immature erythrocytes for the treatment group compared to controls (p<0.01) and exceed laboratory historical control ranges.

Bone marrow cell toxicity is indicated by a substantial and statistically significant dose-related decrease in the proportion of immature erythrocytes (p < 0.01).

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes
Remarks:
lethargy, piloerection, partially closed eyes, brown staining
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid

Any other information on results incl. tables

Treatment

Exposure level

Percent Immature Erythrocytes

Number of micronucleated cells per 2000 Immature Erythrocytes

Number of micronucleated cells per 2000 Mature Erythrocytes

Negative control

0

31

0.1

0.6

Dimethyl glutarate

0.5 mg/L

32

0.4

0.0

 

1.0 mg/L

31

0.4

0.3

 

2.0 mg/L

32

0.2

0.6

Cyclophosphamide

20 mg/kg

27

5.9 (p<0.001)

0.0

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
Dimethyl glutarate does not show any evidence of causing chromosomal damage or bone marrow cell toxicity when administered by whole body inhalation exposure.
Executive summary:

Dimethyl glutarate was administered to F344 rats by whole body inhalation to measure the potential to form micronuclei in bone marrow. Animals were exposed to 0, 0.5. 1.0 and 2.0 mg/l ( analyzed as 0, 0.545, 0.807, and 2.298 mg/L) for 6 hours per day for 2 consecutive days. A positive control group received 20 mg/kg of cyclophophamide by gastric intubation. The were some incidence of weight loss but not considered significant as well as clinical sign (lethargy, partially closed eyes, piloerection, smacking mouth, brown staining of snout and jaws, and oily fur).

Bone marrow smears were obtained 24 hours after exposure from treated and control animals. Smears were were evaluated for the presence of micronuclei in 2000 immature erythrocytes. The proportion of immature erythrocytes was assessed by examination of at least 1000 erythrocytes.

No statistically significant increases in the frequency of micronucleated immature erythrocytes and no substantial decrease in the proportion of immature erythrocytes were observe in dimethyl glutarate-treated animals.

Dimethyl glutarate does not show any evidence of causing chromosomal damage or bone marrow cell toxicity when administered by whole body inhalation exposure.