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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: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP compliant guideline study, available as unpublished report, no restrictions, fully adequate for assessment.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1990
Report Date:
1990

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 478 (Genetic Toxicology: Rodent Dominant Lethal Test)
GLP compliance:
yes
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): 2-METHYLIMIDAZOL
- Analytical purity: 98.6%
- Batch No.: Fis 4/137/2

Test animals

Species:
mouse
Strain:
NMRI
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: BRL, Biological Research Laboratories Ltd. (Wölferweg 4, CH 4414 Füllinsdorf, Switzerland)
- Age at study initiation: 8 weeks
- Weight at study initiation: 30-40 g (males) and 20-30 g (females)
- Assigned to test groups randomly: yes
- Housing: for mating, the animais were housed overnight in Makrolon cage type II in the ratio 1 male : 1 female. During the day, males were housed singly (Makrolon cage type II). After mating the females, the males were housed individually (Makrolon type II) prior to the next mating period. After 4 days or after mating, females were housed for a maximum of 10 per cage (Makrolon cages type III) until necropsy. All cages were equiped with wire mesh tops and standardized granulated softwood bedding (Lignocel, Schill AG, CH 4132 Muttenz, Switzerland).
- Diet: pelleted standard Kliba 343 rat/mouse maintenance diet (Kliba, Klingentalmuehle AG, CM 4303 Kaiseraugst, Switzerland), ad libitum
- Water: ad libitum.
- Acclimation period: 1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3
- Humidity (%): 40-70
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:
intraperitoneal
Vehicle:
- Vehicle used: water
Details on exposure:
DOSING SOLUTIONS: all groups received a volume of 5 mL/kg body weight with adjustment of individual volume to the actual body weight. The control articles and the test article were administered once on the day of starting pairing.

PREPARATION OF DOSING SOLUTIONS: The test article was weighed into a glass beaker on a tared precision balance (Mettler PE 360) and the vehicle added (w/v). The mixtures were prepared prior to administration using a homogenizer.
Duration of treatment / exposure:
single intraperitoneal injection
Frequency of treatment:
single intraperitoneal injection
Post exposure period:
14 days
Doses / concentrations
Remarks:
Doses / Concentrations:
90 and 180 mg/kg bw
Basis:
other: actual received
No. of animals per sex per dose:
40 treated males and 240 untreated females
Control animals:
yes, concurrent vehicle
Positive control(s):
methylmethanesulfonate in NaCl solution
- Route of administration: intraperitoneal
- Dose: 80 mg/kg bw

Examinations

Tissues and cell types examined:
FEMALES:
On day 14 after mating, female mlce were killed by cervical dislocation, autopsled and the uteri examined for the number of live embryos and embryonic deaths. In addition, uteri without visible implantatlons were placed into a solution of ammonium sulphide to visualize early embryonlc resorptions (Salewski, E., Arch. Exp. Path. Pharmak. 247 (1964), 367 - 386).

MALES:
After the last mating period, males were killed by cervical dlslocation and discarded.
Evaluation criteria:
The following formula (Ehling, U. H., et al., 1978) was used for the calculation of dominant lethal factors:

FL% = (1 - (live implants per female of the test group/live implants per female of the control group)) x 100

This formula has the advantage that the spontaneous lethal rate, which is independent of the treatment and is specific for each mouse strain, is eliminated so that the proportion of lethal effects induced by the treatment is directly evident.

Male and female fertility indices, mating-, pregnancy-, implantation ratios and number of percentages of live and dead embryos were calculated and reported for each week. Dam and sire were identified on all data.
Statistics:
The following statistical methods were used to analyze body weights data of the males and the proportion of live embryos and embryonic deaths at each mating period.
- Univariate one-way analysis of variance was used to assess the significance of intergroup differences.
- If the variables could be assumed to follow a normal distribution, the Dunnett-test (many-one t-test), based on a pooled variance estimate, was applied for the comparison between the treated groups and the control group.
- Fisher's Exact test for 2x2 tables was applied if the variables could be dichotomized without loss of information.
Individual values, means, standard deviations and t-statistics were rounded off before printing.

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
- The single intrapenitoneal injection of the substance to male mice caused ruffled fur during a period of fifteen days at the 180 mg/kg bw dose level. No further reaction to treatment was observed.
- The mean body weight gain was similar in all groups during the entire study.
- The calculated dominant lethal factors as well as the mating, pregnancy and implantation ratios yielded no test article-related differences from both
dose groups in comparison wlth the vehicle control group. All differences noted were within the normal range of variations for animals of this strain and age.

Applicant's summary and conclusion