Isobutyl methacrylate

Genetic toxicity: in vivo

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: see 'Remark'

Remarks:

DATA QUALITY: Study was conducted in accordance with a recognized scientific procedure for determining the adverse effects of a test substance in the Mouse Micronucleus Cytogenetic Assay following GLP regulations. Positive control used was one recognized and required in contemporary mutagenic assays; and also confirmed the sensitivity of the test procedure to detect an increase in micronuclei in vivo. The study meets national and international scientific standards and provides sufficient information to support the conclusions regarding the mutagenic findings demonstrated from the study data.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1989

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

Test material information

Constituent 1

Reference substance name:

Isobutyl methacrylate

EC Number:

202-613-0

EC Name:

Isobutyl methacrylate

Cas Number:

97-86-9

Molecular formula:

C8H14O2

IUPAC Name:

isobutyl methacrylate

Specific details on test material used for the study:

Isobutylmethacrylate; 99.8% purity; colorless liquid.

Test animals

Species:

mouse

Strain:

NMRI

Sex:

male/female

Details on test animals or test system and environmental conditions:

NMRI Mice, 12 weeks old at initiation, males and females  weighing approximately 30 grams; housed singly.

Administration / exposure

Route of administration:

oral: gavage

Details on exposure:

In a pre-experiment, 4 animals (2 m  and 2 f) per dose received a single oral dose of 5000 mg/kg body weight  
of the test material suspended in 1 % CMC (carboxymethylcellulose). A  dose volume of 10 ml/kg was used. These 
animals displayed toxic symptoms:  apathy, reduced activity and closed eyelids. 

In the full experiment, 6  males and 6 females were assigned to each test group (negative control,  positive control 
and test material), examined at 24, 48 and 72 hours  post-treatment. A single dose of 5000 mg/kg was given orally.

Duration of treatment / exposure:

single dose

Doses / concentrations

Remarks:

Doses / Concentrations:
5000 mg/kg (1 % in CMC Carboxymethycellulose)
Basis:

No. of animals per sex per dose:

six/sex/dose

Control animals:

yes, concurrent vehicle

Positive control(s):

 Cyclophosphamide (CP): 40 mg/kg given orally as a single dose  

Examinations

Tissues and cell types examined:

Tissues and Cells Examined: 
femur bone marrow      
Number of polychromatic erythrocytes (PCEs) examined per animal 1000        
Number of normochromatic erythrocytes (NCEs) examined per animal 1000         
Proportion of polychromatic erythrocytes to normochromatic erythrocytes,  per 1000 PCEs.

Details of tissue and slide preparation:

Sampling after 24, 48 and 72 hours.

positive control sampled after 48 hours.

Details of slide preparation: 24, 48, and 72 hrs after dose  administration 5M/5/F per test article-treated and vehicle control groups  are sacrificed by cervical dislocation. Positive control group was  sacrificed 24 hrs after dosing, only. Immediately after sacrifice, femurs  are exposed and bone marrow aspirated into a syringe containing fetal  bovine serum and transferred to a centrifuge tube where the bone marrow  cells are pelleted by centrifugation and the supernatant drawn off. Cells  resuspended by aspiration with a capillary pipette and a small drop of  the bone marrow suspension is spread onto a clean glass slide, air dried,  fixed by dipping in methanol, and stained with May-Gruenwald-Giemsa.  Note: an extra male and female mouse per dose was retained in case an  animal died during the gavage process.

Results and discussion

Test results

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

2 males and 1  female died during the 48 hr assay period, and 1 female died during the  72 hr period.

Positive controls validity:

valid

Additional information on results:

Results from Pilot Toxicity Assay showed no mortality at  5000 mg/kg. Based upon these results the high dose 
for the micronucleus  test was set at 5000 mg/kg. 

In the micronucleus test, 2 males and 1  female died during the 48 hr assay period, and 1 female died during the 
72 hr period. The number of micronucleated PCEs per 1000 cells in  test-article treated groups was not statistically 
increased relative to  the vehicle control in either sex, regardless of collection time. The  positive control (CP) 
induced a significant increase in micronucleated  PCEs in both sexes. At 24 hours, the number of PCEs with 
micronuclei was  0.09 % (vehicle), 0.13 % (test material), and 1.06 % (positive control).  At 48 and 72 hrs the 
results for vehicle versus test material were  0.14-0.09 % and 0.06-0.08 %, respectively. A cytotoxic effect was 
evidenced by a reduction in number of  polychromatic erythrocytes (PCE) in relation to the normochromatic  
erythrocytes (NCE). A score of 1,000 PCE was determined for each animal  revealing no indication for a genotoxic 
activity of i-BMA in vivo.

Applicant's summary and conclusion

Conclusions:

The test material was negative (not clastogenic) in the micronucleus test using male and female NMRI mice.

Executive summary:

In a valid guideline study, the test material was negative (not clastogenic) in the micronucleus test using male and female NMRI mice.