Methylhydrazine

Endpoint summary

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

Reference

Reference 1

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

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.

Reference 2

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

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.

Reference 3

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

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

Reference

Reference 1

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

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 or test system 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).

Reference 2

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

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 or test system 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.