Methacrylonitrile

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

Study period:

no data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Comparable to guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2000

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Deviations:

no

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Methacrylonitrile

EC Number:

204-817-5

EC Name:

Methacrylonitrile

Cas Number:

126-98-7

Molecular formula:

C4H5N

IUPAC Name:

2-methylprop-2-enenitrile

Details on test material:

- Name of test material (as cited in study report): Methacrylonitrile
- Substance type: organic aliphatic nitrile
- Physical state: liquid, colorless
- Analytical purity: 99.9%
- Lot/batch No.: JY00427ET
- Supplier: Aldrich Chemical Company, Milwaukee, WI
- Stability under test conditions: no significant decomposition was observed by gas chromatographical analysis during the study
- Storage condition of test material: protected from light at 5 degrees Centigrade

Test animals

Species:

other: rat and mice

Strain:

not specified

Sex:

male

Details on test animals or test system and environmental conditions:

no data

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

Corn oil

Details on exposure:

No data

Duration of treatment / exposure:

96h

Frequency of treatment:

3 injections at 24h intervals

Post exposure period:

24h after the last injection

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0, 12, 25, 50, 100, and 200 mg/kg bw
Basis:
nominal conc.
for rats

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0, 6.25, 12.5, and 25 mg/kg bw
Basis:
nominal conc.
for mice

No. of animals per sex per dose:

Five animals per dose group

Control animals:

yes, concurrent vehicle

Positive control(s):

cyclophosphamide

Examinations

Tissues and cell types examined:

Polychromatic erythrocytes (PCEs) derived from bone marrow

Details of tissue and slide preparation:

The animals were killed 24 hours after the third injection, and slides were prepared from bone marrow cells obtained from the femurs. Air-dried smears were fixed and stained; 2,000 polychromatic erythrocytes (PCEs) were scored for the frequency of micronucleated cells in each of up to five animals per dose group.

Evaluation criteria:

In the used micronucleus test, an individual trial is considered positive if the trend test P value is less than or equal to 0.025 or if the P value for any single dose group is less than or equal to 0.025 divided by the number of dose groups.

Statistics:

The frequency of micronucleated cells among PCEs was analyzed by a statistical software package that tested for increasing trend over dose groups with a one-tailed Cochran-Armitage trend test, followed by pairwise comparisons between each dosed group and the control group (ILS, 1990).

Results and discussion

Test results

Sex:

male

Genotoxicity:

negative

Remarks:

rats and mice

Toxicity:

not specified

Vehicle controls validity:

valid

Negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

In a male rat bone marrow micronucleus test, an initial trial showed a significant induction of micronuclei in the 25 mg/kg group; however, a second trial showed no induction of micronuclei in bone marrow polychromatic erythrocytes, and the test was determined to be negative overall . Also, no increase in the frequency of micronucleated polychromatic erythrocytes was observed in the bone marrow of male mice treated with 6.25 to 25 mg/kg methacrylonitrile.

Any other information on results incl. tables

Table 1: Induction of Micronuclei in Bone Marrow Polychromatic Erythrocytes of Male Rats Treated with Methacrylonitrile by Intraperitoneal Injection

Compound	Dose [mg/kg bw]	Number of rats scored	Micronucleolated PCEs/1000 PCEs^b	P value^c
Trial 1
Corn oil^d		4	0.25±0.14
Cyclophosphamide^e	25	4	6.00±0.98	0.0000
Methacrylonitrile	25	5	1.40±0.37	0.0050
	50	3	0.83±0.44	0.0633
	100	2^f	0.50±0.50
	200		Lethal
				P=0.086^g
Trial 2
Corn oil^d		5	1.80±0.46
Cyclophosphamide^e	25	3	4.00±0.29	0.0042
Methacrylonitrile	12	5	1.10±0.37	0.9033
	25	5	1.60±0.29	0.6343
	50		Lethal
				P=0.643^g

PCE=polychromatic erythrocyte

^bMean ± standard error

^cPairwise comparison with the solvent control

^dSolvent control

^ePositive control

^fOmitted from statistical analysis; invalid data point due to poor survivability

^gSignificance of micronucleated PCEs/1,000 PCEs tested by the one-tailed trend test, significant at P≤0.025

 

Table 2: Induction of Micronuclei in Bone Marrow Polychromatic Erythrocytes of Male Mice Treated with Methacrylonitrile by Intraperitoneal Injection

Compound	Dose [mg/kg bw]	Number of rats scored	Micronucleolated PCEs/1000 PCEs^b	P value
Trial 1
Corn oil^c		5	1.00±0.16
Cyclophosphamide^d	25	5	3.30±0.60
Methacrylonitrile	6.25	5	1.60±0.62
	12.5	5	1.60±1.23
	25	3	1.17±1.17
				P=0.450^e

PCE=polychromatic erythrocyte

^bMean ± standard error

^cSolvent control

^dPositive control

^eSignificance of micronucleated PCEs/1,000 PCEs tested by a one-tailed trend test, significant at P≤0.025

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
Using an in vivo micronucleus test in male rats and mice, no evidence of in vivo genotoxicity of methacrylonitrile could be shown.