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Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

An in vitro microbial assay, an in vitro mouse lymphoma assay, an in vitro unscheduled DNA synthesis assay and two in vivo tests (dominant lethal assays, in rats and mice) were available.

Methylhydrazine was mutagenic only in an activation, in vitro microbial reversion test if the test was conducted as suspension test and not if conducted as standard plate tests. Except for this, there was no indication of genetic activity in any of the other tests.

Link to relevant study records

Referenceopen allclose all

Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The publication is a summary of several mutagenicity studies performed on methylhydrazine. The summarized report has been reviewed by the Information Office (OI) and is releasable to the National Technical Information Service (NTIS). Some data are absent (GLP statement, data on the test item(batch number, expiry date...)).
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
GLP compliance:
not specified
Type of assay:
other: bacterial reverse mutation assay (Salmonella typhimurium and Escherichia coli)
Target gene:
histidine
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Species / strain / cell type:
S. typhimurium, other: G-46
Species / strain / cell type:
S. typhimurium TA 1538
Species / strain / cell type:
E. coli WP2 uvr A
Species / strain / cell type:
Saccharomyces cerevisiae
Metabolic activation:
with and without
Metabolic activation system:
mouse hepatic microsomes
Test concentrations with justification for top dose:
In agar assay without activation:
0.0001, 0.001, 0.01, 1 and 5 µL/plate
In agar assay with activation:
0.01, 0.1, 1 and 5 µL/plate
Suspension assay with activation:
1 and 5 µL/mL
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: direct acting mutagens were employed in non activation assays, mutagens requiring microsomal activation were used in activation assays
Remarks:
Dimethylnitrosamine was used as the positive control compound in the suspension assay
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation) + additional assay with S. Typhimurium TA-1535 in suspension

DURATION:
- Exposure duration: 48 to 72 hours for plate incorporation assays, 1 hour for suspension assay
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Species / strain:
S. typhimurium, other: G-46
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Species / strain:
S. typhimurium TA 1538
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Species / strain:
Saccharomyces cerevisiae
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
In the suspension assay, MH was found to be positive. Mutagenic activity was observed at MH concentrations of 1 µL and 5 µL after a 60-minute incubation with a mouse liver activation system.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.
Conclusions:
Interpretation of results (migrated information):
negative

There were no clear indications of mutagenic activity by MH in any of the microbial assays performed. The toxicity of MH for bacterial and yeast was high and concentrations of 10 µL/plate were too toxic to use.
MH was mutagenic in activation, microbial reversion test conducted as a suspension test.
Endpoint:
in vitro gene mutation study in mammalian cells
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The publication is a summary of several mutagenicity studies performed on methylhydrazine. The summarized report has been reviewed by the Information Office (OI) and is releasable to the National Technical Information Service (NTIS). Some data are absent (GLP statement, data on the test item(batch number, expiry date...)).
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
Principles of method if other than guideline:
The procedure used was a modification of that reported by Clive and Spector.
GLP compliance:
not specified
Type of assay:
mammalian cell gene mutation assay
Target gene:
thymidine kinase locus
Species / strain / cell type:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Metabolic activation system:
mouse liver microsomes
Test concentrations with justification for top dose:
Without activation:
0.0005, 0.001, 0.05 and 0.1 µL/mL
With activation:
0.001, 0.005, 0.01 and 0.05
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: direct acting mutagens were employed in non activation assays, mutagens requiring microsomal activation were used in activation assays
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium

DURATION:
- Exposure duration: 5 hours
- Expression time (cells in growth medium): 3 days

MUTATION FREQUENCY:
Mutation frequency was = (mutant counts)/(viable counts) x 10-4

DETERMINATION OF CYTOTOXICITY:
- Method: measure of loss in growth potential of the cells induced by a five-hour exposure to methylhydrazine
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.
Conclusions:
Interpretation of results (migrated information):
negative

In a mammalian cell gene mutation test, methylhydrazine was clearly non genotoxic, with and without activation.
Endpoint:
in vitro cytogenicity / micronucleus study
Remarks:
Type of genotoxicity: DNA damage and/or repair
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The publication is a summary of several mutagenicity studies performed on methylhydrazine. The summarized report has been reviewed by the Information Office (OI) and is releasable to the National Technical Information Service (NTIS). Some data are absent (GLP statement, data on the test item(batch number, expiry date...)). Exposure duration was not reported.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 482 (Genetic Toxicology: DNA Damage and Repair, Unscheduled DNA Synthesis in Mammalian Cells In Vitro)
GLP compliance:
not specified
Type of assay:
DNA damage and repair assay, unscheduled DNA synthesis in mammalian cells in vitro
Target gene:
Not applicable.
Species / strain / cell type:
mammalian cell line, other: human diploid embryonic lung cells (WI-38)
Metabolic activation:
with and without
Metabolic activation system:
mouse liver microsomes
Test concentrations with justification for top dose:
With and without activation:
0.1, 0.5 and 1.0 µg/mL
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: direct acting mutagens (MNNG) were employed in non activation assays, mutagens requiring microsomal activation (2-acetylaminofluorene) were used in activation assays
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium

DURATION
- Exposure duration: not indicated
- Expression time (cells in growth medium): untill confluency was reached

DETERMINATION OF CYTOTOXICITY
- Method: other: toxicity was monitored visually by altered cell morphology and adhesion.
Species / strain:
mammalian cell line, other:
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
not specified
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.
Conclusions:
Interpretation of results (migrated information):
negative

The results were negative, but there was no information about exposure duration. Moreover, no data were available on cytotoxicity: it was impossible to determine if cytotoxicity was achieved in the high dose level (a preliminary test was performed to determine cytotoxicity and dose-levels of the main test, but the results are not available).
Endpoint conclusion
Endpoint conclusion:
adverse effect observed (positive)

Genetic toxicity in vivo

Link to relevant study records

Referenceopen allclose all

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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The publication is a summary of several mutagenicity studies performed on methylhydrazine. The summarized report has been reviewed by the Information Office (OI) and is releasable to the National Technical Information Service (NTIS). Some data are absent (GLP statement, data on the test item(batch number, expiry date), environmental conditions...).
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 478 (Genetic Toxicology: Rodent Dominant Lethal Test)
GLP compliance:
not specified
Type of assay:
rodent dominant lethal assay
Species:
mouse
Strain:
ICR
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: 7 to 8 week-old
- Weight at study initiation: 30 +/- 2.5 g
- Fasting period before study: no data
- Housing: 5 per cages
- Diet (e.g. ad libitum): 4% fat diet
- Water (e.g. ad libitum): acidified water
- Acclimation period: no data

ENVIRONMENTAL CONDITIONS
No data
Route of administration:
intraperitoneal
Vehicle:
- Vehicle(s)/solvent(s) used: corn oil or water
Duration of treatment / exposure:
Five days
Frequency of treatment:
Daily
Post exposure period:
8 weeks
Remarks:
Doses / Concentrations:
0.26, 0.86 and 2.6 mg/kg/day
Basis:
no data
No. of animals per sex per dose:
10 males per dose-level
Control animals:
yes, concurrent vehicle
Positive control(s):
- Triethylenemelamine
- Route of administration: intraperitoneal
- Doses / concentrations: 0.3 mg/kg in 0.85% saline
Sex:
male
Genotoxicity:
negative
Toxicity:
not specified
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid
Conclusions:
Interpretation of results (migrated information): negative
Dominant lethality, which is indicated by a high percentage of dead implants to total implants, was not demonstrated (a clear dominant lethal effect was observed with the positive control but only in the first 3 weeks of observation).
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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The publication is a summary of several mutagenicity studies performed on methylhydrazine. The summarized report has been reviewed by the Information Office (OI) and is releasable to the National Technical Information Service (NTIS). Some data are absent (GLP statement, data on the test item(batch number, expiry date...)).
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 478 (Genetic Toxicology: Rodent Dominant Lethal Test)
GLP compliance:
not specified
Type of assay:
rodent dominant lethal assay
Species:
rat
Strain:
Sprague-Dawley
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: 10 to 12 week-old
- Weight at study initiation: 325 +/- 25 g
- Fasting period before study: not indicated
- Housing: 5 per cages
- Diet (e.g. ad libitum): 4% fat diet
- Water (e.g. ad libitum): acidified water
- Acclimation period: no data

ENVIRONMENTAL CONDITIONS
- no data
Route of administration:
intraperitoneal
Vehicle:
- Vehicle(s)/solvent(s) used: corn oil or water
Duration of treatment / exposure:
5 days
Frequency of treatment:
daily
Post exposure period:
7 weeks
Remarks:
Doses / Concentrations:
0.215, 0.72 and 2.15 mg/kg/day
Basis:
no data
No. of animals per sex per dose:
5 males per dose-level
Control animals:
yes, concurrent vehicle
Positive control(s):
- Triethylenemelamine
- Route of administration: intraperitoneal
- Doses / concentrations: 0.3 mg/kg in 0.85% saline
Sex:
male
Genotoxicity:
negative
Toxicity:
not specified
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid
Conclusions:
Interpretation of results (migrated information): negative
Methylhydrazine was not considered to be genotoxic in a dominant lethal assay in rats. Statistically significant high ratio of dead to total implants was observed in week 7, but it was associated with the absence of dead implants in controls. Moreover this ratio was less than ratios calculated in positive controls during weeks 1 to 5. Therefore this observation was not considered to be biologically relevant.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

Methylhydrazine was mutagenic only in an activation, in vitro microbial reversion test if the test was conducted as suspension test and not if conducted as standard plate tests. Except for this, there was no indication of genetic activity in any of the other tests conducted in a three tier test initiated by Toxicology Branch, Toxic Hazards Division, Aerospace Medical Research Laboratory.

Justification for classification or non-classification

As mutagenic activity was only demonstrated in one strain of Salmonella Typhimurium in a reverse bacterial gene mutation test in suspension conditions, monomethylhydrazine is not considered to have mutagenic potential and shall not be classified for mutagenicity.