But-1-ene

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP compliant, guideline study, available as unpublished report, fully adequate for assessment

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1990

Report date:

1990

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Principles of method if other than guideline:

not applicable

GLP compliance:

yes (incl. QA statement)

Type of assay:

micronucleus assay

Test material

Test material information

Constituent 1

Reference substance name:

2-methylpropene

EC Number:

204-066-3

EC Name:

2-methylpropene

Cas Number:

115-11-7

Molecular formula:

C4H8

IUPAC Name:

2-methylprop-1-ene

Constituent 2

Reference substance name:

isobutylene

IUPAC Name:

isobutylene

Constituent 3

Reference substance name:

MRD-89-360

IUPAC Name:

MRD-89-360

Details on test material:

- Name of test material (as cited in study report): MRD-89-360
- Physical state: Colourless gas
- Analytical purity: Considered 100% pure
- Storage condition of test material: Room temperature

Test animals

Species:

mouse

Strain:

B6C3F1

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc., Shaver Road, Portage, Michigan 49081, USA
- Age at study initiation: approx. 6-7 weeks
- Weight at study initiation: 20-26 g (Day -2)
- Assigned to test groups randomly: no (using a computer generated, body weight sorting program)
- Housing: Individually in suspended stainless steel cages.
- Diet: Purina Certified Rodent Chow #5002 (pellets) (Ralston Purina Company) ad libitum (except during exposure)
- Water: Mains water ad libitum (except during exposure)
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature: 68-76°F
- Humidity: 40-70%
- Air changes (per hr): Not reported
- Photoperiod: 12hrs dark / 12hrs light

IN-LIFE DATES: From: 29 November 1989 To: 1 December 1990

Administration / exposure

Route of administration:

inhalation

Vehicle:

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

Details on exposure:

TYPE OF INHALATION EXPOSURE: whole body

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
The test material was delivered from a cylinder via a pressure regulator to a 1/4" coil of copper tubing submerged in a slightly heated water bath. The test material volatilised within the copper coil, entered a regulator to reduce pressure, and the resulting vapours were metered to the exposure chambers. The exposure chambers operated at an exhaust flow rate of 200 L/min, providing 1 air change every 5 mins and a theoretical equilibration time (T99) of 23 mins. The test and control groups were each contained in 1m3 stainless steel and glass chambers.

TEST ATMOSPHERE
- Brief description of analytical method used: Gas chromatography
- Samples taken from breathing zone: yes

Duration of treatment / exposure:

2 days

Frequency of treatment:

6 hours/day

Post exposure period:

1 day

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
1000, 3260, 10000 ppm
Basis:
other: target exposure concentrations

Doses / concentrations 2

Remarks:

Doses / Concentrations:
1076, 3269, 10042 ppm
Basis:
analytical conc.

No. of animals per sex per dose:

10 males per group

Control animals:

yes, sham-exposed

Positive control(s):

MRD-89-362 (1,3 butadiene)
- Route of administration: inhalation
- Doses / concentrations: 1000 ppm

Examinations

Tissues and cell types examined:

polychromatic erythrocytes of the bone marrow of B6C3F1 mice

Details of tissue and slide preparation:

TREATMENT AND SAMPLING TIMES: Animals were killed approximately 24 hours after second exposure period. Immediately after death, both femurs were removed. The bone marrow was then removed and suspended in foetal bovine serum. After the suspension was centrifuged, the pellet was resuspended and smears were prepared (two slides per animal).

DETAILS OF SLIDE PREPARATION: Slides were stained using acridine orange

Evaluation criteria:

Polychromatic erythrocytes (PCE), normochromatic erythrocytes (NCE) and micronuclei identified by stain. Additional criteria for scoring micronuclei are a circular appearance and a diameter between 1/20 and 1/5 of the cell's diameter. 1000 polychromatic erythrocytes (PCE) from each animal were examined for micronuclei, and the ratio of PCE's to NCE's was determined for each animal by counting 1000 erythrocytes (PCE's and NCE's).

Statistics:

Statistical analysis included calculation of means and standard deviations of the micronuclei data and a test of equality of group means by a standard one way analysis of variance at each time period. When the ANOVA was significant, comparisons of control to dosed group means were by Duncan's Multiple Range Test. A standard regression analysis was performed to test for a dose response. Residuals from the ANOVA were analyzed for normality by Wilk's Criterion. The residuals were normally distributed (at the 0.01 level of significance) in more than 25% of the analyses. Therefore nonparametric analyses were not performed.

Results and discussion

Test results

Sex:

male

Genotoxicity:

negative

Toxicity:

no effects

Vehicle controls validity:

valid

Negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

Positive and negative controls gave the expected results. A statistically significant decrease in the percentages of polychromatic erythrocytes (a measure of toxicity) was also observed.

Any other information on results incl. tables

none

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): negative
Isobutylene (2-methylpropene) was negative in the mouse bone-marrow micronucleus test.

Executive summary:

Mice were exposed to isobutylene (2-methylpropene) at target concentrations up to 10000 ppm (22948 mg/m3) for 2 days (6 hours/day). A statistically significant increase in micronucleus formation in mouse bone marrow was not observed therefore isobutylene was not clastogenic in mouse bone marrow. Positive and negative control compounds gave the expected results indicating that the method was robust.