3-(methylthio)propionaldehyde

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:

1999-11-18 to 2000-01-27

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2000

Report date:

2000

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Version / remarks:

adopted 21 Jul 1997

Deviations:

yes

Remarks:

high mortality at 200 mg/kg bw/day, thus only 2 valid dose levels were used

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: ICH Tripartite Harmonised Guideline on Genotoxicity: Specific Aspects of Regulatory Tests

Version / remarks:

adopted 1995

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: Japanese MAFF

Version / remarks:

adopted 1990

Test guideline 4

Qualifier:

according to guideline

Guideline:

other: EPA OPPTS-42193 Mammalian Eryhtrocyte Micronucleus Test

Version / remarks:

adopted Aug 1997

GLP compliance:

yes

Type of assay:

mammalian erythrocyte micronucleus test

Test material

Test material information

Constituent 1

Reference substance name:

3-(methylthio)propionaldehyde

EC Number:

221-882-5

EC Name:

3-(methylthio)propionaldehyde

Cas Number:

3268-49-3

Molecular formula:

C4H8OS

IUPAC Name:

3-(methylthio)propionaldehyde

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, Margate, UK
- Weight at study initiation: 22 - 31 g (males) and 21 - 27 g (females)
- Assigned to test groups randomly: yes
- Housing: in groups of no more than three animals of the same sex in appropriate caging, cleaned and dried before use
- Diet: laboratory chow diet (Special Diets Services Ltd), ad libitum
- Water: tap water, ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 - 24
- Humidity (%): 54 - 61
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

intraperitoneal

Vehicle:

- Vehicle(s)/solvent(s) used: corn oil
- Concentration of test material in vehicle: 2.5, 5.0 and 10.0 mg/mL

Details on exposure:

PREPARATION OF DOSING SOLUTIONS: Dosing formulations were made by mixing the test item with corn oil. Dilutions were made using corn oil. The test article formulations were inverted periodically during dosing and used within approximately 2.75 hours of initial formulation.

Duration of treatment / exposure:

2 days

Frequency of treatment:

administration of 2 doses, 24 h apart

Post exposure period:

24 h

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

50 mg/kg bw/day (actual dose received)

Doses / concentrations 2

Dose / conc.:

100 mg/kg bw/day (actual dose received)

Doses / concentrations 3

Dose / conc.:

200 mg/kg bw/day (actual dose received)

No. of animals per sex per dose:

6

Control animals:

yes, concurrent vehicle

Positive control(s):

cyclophosphamide
- Route of administration: intraperitoneal injection
- Doses / concentrations: 40 mg/kg bw, single administration

Examinations

Tissues and cell types examined:

Tissue: bone marrow
Cell type: bone marrow cells

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION:
A range finding study was performed to find the maximum tolerated dose.

TREATMENT AND SAMPLING TIMES:
Two single doses were administered, one on each of two consecutive days. Sampling was performed 24 h after the last dose.

DETAILS OF SLIDE PREPARATION:
The cells were centrifuged and the serum was aspirated to leave one or two drops and the cell pellet. The pellet was mixed into this small volume of serum and the suspension was dropped on each of two coded slides. Slides were allowed to air-dry and fixed for 5 min in absolute methanol. Finally, the slides were stained with Giemsa (1:6 v/v in distilled water), rinsed, air-dried and cleared in xylene for 3 min.

METHOD OF ANALYSIS:
The proportion of polychromatic (immature, PCE) among total (polychromatic + normochromatic (NCE)) erythrocytes was determined for each animal by counting a total of 1000 erythrocytes (PCE + NCE).
2000 polychromatic erythrocytes were counted per animal to determine the presence of micronuclei.

Evaluation criteria:

A test article is considered as positive in this assay if a statistically significant increase in the frequency of micronucleated PCE occurs at least at one dose, and if the frequency of micronucleated PCE at such a point exceeds the historical vehicle control range.

Results and discussion

Test results

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

clinical signs at 100 and 200 mg/kg bw/day

Vehicle controls validity:

valid

Negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE-FINDING STUDY:
Dose levels were chosen based on an initial range finding study with groups of 3 male and female mice at a dose range of 50 to 400 mg/kg bw/day, once daily for two consecutive days. Death of all animals occured at dose levels of 300 and 400 mg/kg bw/day. Clinical symptoms were observed from 100 mg/kg bw/day. Consequently doses of 50, 100 and 200 mg/kg bw/day were chosen for the main study.

RESULTS OF DEFINITIVE STUDY
- Induction of micronuclei: The test item did not induce a statistically significant increase in the frequency of micronucleated PCEs up to 200 mg/kg bw/day. Group mean frequencies of micronucleated PCE were also similar to that seen in the vehicle controls. The number of micrunucleated PCE of the control animals fell within the historical control rate. The positive control substance induced a statistically significant increase in the frequency of micronucleated PCEs.
- Ratio of PCE/NCE: PCE/NCE ratios of the treated animals were similar to those of the vehicle controls.
- Statistical evaluation: Chi-square test

MORTALITY: Several animals (6/6 males and 2/6 females) of the high dose group died prior to the sampling time.
CLINICAL SIGNS: Clinical symptoms were observed at 100 and 200 mg/kg bw/day. At 100 mg/kg bw/day, lethargy and eye closure were noted. At 200 mg/kg bw/day, the animals showed abnormal breathing, lethargy, eye closure, prostration and abnormal gait.

Applicant's summary and conclusion

Conclusions:

Interpretation of results: negative