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Toxicological information

Genetic toxicity: in vivo

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Administrative data

Endpoint:
in vivo mammalian germ cell study: cytogenicity / chromosome aberration
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1979-10-15 to 1980-05-01
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study is classified as reliable without restrictions because although a GLP certificate was not provided the study seemed well-conducted.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1980
Report Date:
1980

Materials and methods

Test guideline
Qualifier:
no guideline available
GLP compliance:
not specified
Type of assay:
rodent dominant lethal assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): n-hexane
- Physical state: clear liquid
- Analytical purity:
- Impurities (identity and concentrations):
- Composition of test material, percentage of components:
- Isomers composition:
- Purity test date:
- Lot/batch No.:
- Expiration date of the lot/batch:
- Radiochemical purity (if radiolabelling):
- Specific activity (if radiolabelling):
- Locations of the label (if radiolabelling):
- Expiration date of radiochemical substance (if radiolabelling):
- Stability under test conditions:
- Storage condition of test material:
- Other:

Test animals

Species:
mouse
Strain:
CD-1
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River
- Age at study initiation: 11 weeks old
- Assigned to test groups randomly: yes


Administration / exposure

Route of administration:
inhalation: vapour
Vehicle:
- Vehicle(s)/solvent(s) used: filtered air
Details on exposure:
TYPE OF INHALATION EXPOSURE: whole body


GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel and plexiglass chambers of 0.25 cubic meter volume.
- Method of conditioning air: The chambers were operated in a dynamic mode using room air to dilute the test material.
- System of generating particulates/aerosols: The vapor was generated by bubbling dry, oil-free, breathing-quality air through a column of liquid test material in a fritted-glass cylinder gas washing bottle.
- Temperature, humidity, pressure in air chamber:
- Air flow rate: 28.3 L per minute



TEST ATMOSPHERE
- Brief description of analytical method used: Analysis was initially performed using the Scott Model 216 Hydrocarbon Analyzer for the first two weeks. For the remainder of the study period, a Wilks Model 80 Computing Infrared Analyzer was used.
- Samples taken from breathing zone: yes
Duration of treatment / exposure:
8 weeks
Frequency of treatment:
6 hours per day, 5 days per week
Post exposure period:
Following treatment, each male was rested for 2 days and then caged with two unexposed virgin females. At the end of 5 days, these females were removed. This weekly mating sequence was continued for 2 weeks. Each pair of mated females was transferred to a fresh cage, and approximately 14 days after the midweek of being caged with the male, these females were sacrificed. Their uterine contents were examined and scored for numbers of dead and living implants, and total implantations.
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 100, and 400 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
3 male mice per group (a total of 4 groups)
Control animals:
yes, concurrent vehicle
Positive control(s):
- triethylenemelamine
- Route of administration: intraperitoneal injection

Examinations

Evaluation criteria:
Both pre- and post-implantation losses contribute to dominant lethality. The former is reflected in the total number of implantation sites per
pregnant female and strictly measured by the difference between the number of corpora lutea gravidus and the nunter of Implantation sites.
Toxic or physiological effects on sperm may also reduce the number of implantation sites. Therefore, unless subtle physiological effects on sperm can be discounted, pre-implantation loss is not as rigorous an indication of dominant lethality as post-Implantation loss. Corpora lutea are not evaluated in studies using mice.
Dominant lethality is typically determined from: a) a mutation index derived from the ratio of dead to total implants; or b) the number of dead Implants per pregnant female. In interpreting these values It must be remembered that the former measurement reflects both pre- and postimplantation
losses and that the ratio is affected by changes in either the numerator or the denominator. For this reason, the second parameter is perhaps a better indicator of post-implantation loss. This becomes especially so if one concurrently examines the number of living embryos per pregnant female. The two sets of data should be inversely related. In other words, if true dominant lethality is being observed, then a significant increase in the number of dead implants per pregnant female should be accompanied by a significant decrease in the number of living implants per pregnant female.
These ratios are compared with both concurrent and comparable historical control data for significant statistical differences. Dose-related
trends are also looked for, but may not always be found. For example, some compounds such as EMS tested in mice show a threshold value and
then a very steep rise. Certain portions of the response might be missed, depending on the spacing of the dose levels used.
Statistics:
A chi-square tost is used to compare each treatment group and positive control to negative control.

Armitage's trend for linear proportions is used to test whether the fertility index is linearly related to arithmetic or log dose.

The total number of implantations is evaluated by the Student's t-test to determine whether the average number of implantations per pregnant
female for ecch treatment group and the positive control group differs significantly from the negative control group. Dead implantations were evaluated in the same manner.

The average number of corpora lutea per pregnant female is evaluated by t-test to determine whether each treatment group differed significantly from the control group. A regression fit is made for both the arithmetic and logarithmic dose.

Results and discussion

Test results
Sex:
male
Genotoxicity:
negative
Toxicity:
no effects
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
The test substance did not induce dominant lethal mutations in mice at the two tested dose levles. The sensitivity of the assay was confirmed by the significant induction of dominant lethal mutations in the positive control treated with TEM.
Executive summary:

This study determined the effect of inhalation exposure of n-hexane in a dominant lethal mutagenic assay. Groups of 3 male mice were exposed to 0, 100 and 400 ppm of test substance vapor for 6 hrs/day for 5 days for eight weeks. Triethylenemelamine was used as a positive control substance and administered via intraperitoneal injection. n-Hexane does not cause significant increases in either pre- or post- implantation loss of embryos when statistically compared with the negative control. The test substance did not induce dominant lethal mutations in mice at the two tested dose levels. The test substance is not mutagenic.