Dapsone

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:

2001

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2001

Report date:

2001

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

Dapsone

EC Number:

201-248-4

EC Name:

Dapsone

Cas Number:

80-08-0

Molecular formula:

C12H12N2O2S

IUPAC Name:

4,4'-sulfonyldianiline

Details on test material:

Dapsone, batch no. 70522014, white powder, purity 99.69%, stored at 1-10 degrees C in the dark.

Test animals

Species:

mouse

Strain:

CD-1

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River-UK Ltd
- Age at study initiation: 7 weeks
- Weight at study initiation: 26-33g
- Diet (e.g. ad libitum): availabe ad-libitum
- Water (e.g. ad libitum): availabe ad-libitum
- Acclimation period: 8 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21-23 deg C
- Humidity (%): 52-61%
- Photoperiod (hrs dark / hrs light): 12-hour light/12-hour dark cycle

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

1% methylcellulose in water

Details on exposure:

Groups of 8 male mice (as there was no evidence of sex-related difference in toxicity in the range finding test) were used for each dose groups and one control group. Dose levels were 0, 43.75, 87.5, 175 mg/kg bw/day in the main experiment. A positive control group of 8 male mice received 40 mg/kg cyclophosphamide once on day 2 of the experiment.

Duration of treatment / exposure:

2 consecutive days

Frequency of treatment:

daily once

Post exposure period:

none

No. of animals per sex per dose:

8 males per dose (as no evidence of sex-related differences in toxicity was revealed in the range finding test)

Control animals:

yes, concurrent no treatment

Positive control(s):

cyclophosphamide, 40 mg/kg bw once on day 2

Examinations

Tissues and cell types examined:

Bone marrow were analysed for numbers of micronucleated polychromatic erythrocytes.

Details of tissue and slide preparation:

femours were excised and the content washed out with a syringe into 1% fetal bovine serum in RPMI medium

Evaluation criteria:

- Slides had to have at least 1000 scorable cells (PCE and NCE).
Acceptance Criteria:
The assay was considered valid if the following criteria are met:
1) the incidence of micronucleated PCE in the vehicle control group falls within or close to the historical vehicle control range
2) at least seven animals out of each group are available for analysis, and
3) the positive control chemical (CPA) induces a statistically significant increase in the frequency of micronucleated PCE.
Evaluation Criteria:
A test article is considered positive in this assay if:
1) A statistically significant increase in the frequency of micronucleated PCE occurs at least at one dose, and
2) the frequency of micronucleated PCE at such point exceeds the historical vehicle control range.
the frequency of PCE is higher than the historical control range.

Statistics:

Statistics was applied

Results and discussion

Test results

Sex:

male

Genotoxicity:

negative

Toxicity:

yes

Vehicle controls validity:

valid

Positive controls validity:

valid

Additional information on results:

Mice treated with Dapsone at all doses exhibited frequencies of micronucleated PCE which were similar to the values for the vehicle control group and also fell within the normal range. There were no instances of statistically significant increases in micronucleus frequency for any of the groups receiving Dapsone. The mean PCE to NCE ratios of the groups given Dapsone were similar to the negative control value and fell within the historical negative control range.

Applicant's summary and conclusion

Conclusions:

Dapsone did not introduce micronuclei in the polychromatic erythrocytes of the bone marrow in mice treated up to 175 mg/kg/day, at a dose which limited mortality and clinical signs of toxicity were observed.

Executive summary:

Dapsone was assessed for in vivo gentoxicity in a mouse bone marrow micronucleus assay. The potential of Dapsone to induce structural chromosomal damage and aneuploidy, by determining the frequency of micronucleated polychromatic erythrocytes in mouse bone marrow after exposure to 0 (negative control), 43.75, 87.5 and 175 mg/kg bw/day given on two consecutive days by oral gavage to groups of 8 male mice.

In a range finding test, doses from 500 to 1000 mg/kg Dapsone were administered orally by gavage as a suspension in 1% methylcellulose. Groups of three male and three female out-bred, virus-free, CD-1 mice were dosed on two consecutive days (mortality permitting). Observations were made over a two day period following the first administration and signs of toxicity recorded. No difference in toxicity was seen between males and females.

Based on the results of the range finding test, doses of 0, 43.75, 87.5 and 175 mg Dapsone/kg/d were given on two consecutive days to groups of 8 male mice. All surviving animals were killed 24 hours after receiving their final dose and femoral bone marrow smears examined. Slides from all animals were analyzed from the negative control, positive control and Dapsone-treated groups.

All animals were observed after dosing, with clinical signs and mortalities recorded. In the main study, bone marrow smears were analyzed for numbers of micronucleated polychromatic erythrocytes. The ratio of polychromatic erythrocytes to normochromatic (mature) erythrocytes was also recorded.

Negative and positive control group results were all confirmed as valid. Mice treated with Dapsone at all doses exhibited frequencies of micronucleated PCE which were similar to the values for the vehicle control group, and fell into the normal range. There were no instances of statistically significant increased in micronucleus frequency for any of the groups receiving Dapsone. The mean PCE to NCE ratios of the groups given Dapsone were similar to the negative control value and fell within the historical negative control range.

Dapsone did not introduce polychromatic erythrocytes of the bone marrow in mice treated up to 175 mg/kg/day. Limited mortality and clinical signs were observed at this dose.