Cyanamide

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

EPA OPP 84-2

Deviations:

no

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method B.12 (Mutagenicity - In Vivo Mammalian Erythrocyte Micronucleus Test)

Deviations:

not specified

GLP compliance:

yes

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Cyanamide

EC Number:

206-992-3

EC Name:

Cyanamide

Cas Number:

420-04-2

Molecular formula:

CH2N2

IUPAC Name:

cyanamide

Test material form:

other: aqueous solution

Details on test material:

- Test material: Hydrogen cyanamide in aqueous solution
- Appearance: Clear light yellow liquid
- Purity: 53 % w/v
- Lot/Batch number: 7/07/87

Test animals

Species:

mouse

Strain:

ICR

Sex:

male/female

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

- Vehicle(s)/solvent(s) used: water

Duration of treatment / exposure:

Exposure for 24, 48 and 72 hours at all dose levels

Frequency of treatment:

Daily

Post exposure period:

No post exposure period

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

35 mg/kg bw/day (nominal)

Remarks:

the dosis analytical found was 31.44 mg/kg bw/day

Doses / concentrations 2

Dose / conc.:

175 mg/kg bw/day (nominal)

Remarks:

the dosis analytical found was 157.4 mg/ kg bw/day

Doses / concentrations 3

Dose / conc.:

350 mg/kg bw/day (nominal)

Remarks:

the dosis analytical found was 330.5 mg/kg bw/day

No. of animals per sex per dose:

Five mice/sex per dose

Control animals:

yes, concurrent vehicle

Positive control(s):

A positive control triethylenemelamine

Examinations

Tissues and cell types examined:

Polychromatic erythrocytes and normochromatic erythrocytes from the bone marrow

Details of tissue and slide preparation:

Bone marrow smear slides were prepared and stained. Approximately 1000 polychromatic erythrocytes (PCE’s) were examined for the presence of micronuclei. The ratio of poly- to normochromatic erythrocytes was determined to assess inhibition of erythropoesis.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

At the high dose group 3 male animals were found dead after 5 and 20 hours, respectively. All males at this dose level had ruffled coats throughout the duration of the study. All other animals were apparently healthy until the appropriate sacrifice time.

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

A dose rangefinding study was carried out to assess toxicity with dose levels of 75, 150, 300, 450 and 600 mg/kg bw. Based upon the results of this trial the dose levels selected for the micronucleus assay were 35, 175 and 350 mg/kg bw.

The stability of the test substance throughout the study period was shown by reanalysis. The homogeneity was guaranteed by mixing before preparations of the test solutions. The stability of the test substance in water was verified analytically and the following concentrations were determined: 31.44, 157.4 and 330.5 mg/kg bw.

Applicant's summary and conclusion

Conclusions:

Hydrogen cyanamide did not induce micronuclei in polychromatic erythrocytes of mice when orally (by gavage) treated up to 350 mg/kg body weight.

Executive summary:

The ability of hydrogen cyanamide to cause chromosomal damage in vivo was investigated in the mouse micronucleus assay. Male and female ICR mice were dosed orally by gavage with a aqueous solution of Hydrogen cyanamide. Based upon the results of the range finding trial the dose levels selected for the micronucleus assay were 35, 175 and 350 mg/kg bw. The vehicle control as well as the positive control triethylenemelamine were also tested. The stability of the test substance throughout the study period was shown by reanalysis. The homogeneity was guaranteed by mixing before preparations of the test solutions. The stability of the test substance in water was verified analytically and the following concentrations were determined: 31.44, 157.4 and 330.5 mg/kg.

Five mice/sex were exposed for 24, 48 and 72 hours at all dose levels. Only one sampling time, 24 hours after treatment, was performed with the negative and the positive control. A second group of animals was also assigned to the study and was dosed with the high dose of the test article. These animals were only used in the assay as replacements for any which died in the primary dose group.

Bone marrow smear slides were prepared and stained. Approximately 1000 polychromatic erythrocytes (PCE’s) were examined for the presence of micronuclei. The ratio of poly- to normochromatic erythrocytes was determined to assess inhibition of erythropoesis and all animals were examined after dosing and periodically throughout the duration of the study for toxic effects and/or mortalities.

At the high dose group 3 male animals were found dead after 5 and 20 hours, respectively. All males at this dose level had ruffled coats throughout the duration of the study. All other animals were apparently healthy until the appropriate sacrifice time. No significant changes in the ration of NCE´s to PCE´s were observed. The test substance, hydrogen cyanamide, induced no significant increases in micronucleated polychromatic erythrocytes over the levels observed in the negative controls in either sex or at any sampling interval. The positive control, triethylenmelamine, induced significant increases in micronucleated PCEs in both sexes.

It can be concluded that hydrogen cyanamide did not induce micronuclei in polychromatic erythrocytes of mice when orally (by gavage) treated up to 350 mg/kg body weight.