Registration Dossier

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:
16.07.2001-13.11.2001
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP Guideline study (OECD)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report Date:
2001

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
GLP compliance:
yes (incl. certificate)
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Isobutyl acrylate
- Analytical purity: > 99.5 %
- Lot/batch No.: S 122-01-GA
- Storage condition of test material: refrigeratror, protected from light

Test animals

Species:
mouse
Strain:
NMRI
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: RCC Ltd. Biotechnology and Animal Breeding Division; CH-4414 Fuellinsdorf
- Age at study initiation: 8-10 weeks
- Weight at study initiation: males: mean 44.9 g; females: mean 33.6 g
- Housing: single
- Diet: pelleted standard diet, ad libitum
- Water: Tap water ad libitum



ENVIRONMENTAL CONDITIONS
- Temperature (°C): 24 +/- 4
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
intraperitoneal
Vehicle:
- Vehicle(s)/solvent(s) used: olive oil, O1500, Sigma-Aldrich Vertriebs-GmbH
- Amount of vehicle: 10 mL/kg
Duration of treatment / exposure:
single injection; harvesting of cells 24 and 48 hours after administration of test substance
Frequency of treatment:
single treatment
Doses / concentrations
Remarks:
Doses / Concentrations:
males: 0, 250, 500, 1000 mg/kg bw (24 hours harvesting) and 0, 1000 mg/kg bw (48 hours harvesting); females: 0, 312.5, 625, 1250 mg/kg bw (24 hours harvesting) and 0, 1250 mg/kg bw (48 hours harvesting)
Basis:
other: injected intraperitoneally
No. of animals per sex per dose:
5
Control animals:
yes, concurrent vehicle
yes, historical
Positive control(s):
cyclophosphamide, 40 mg/kg bw, i.p.

Examinations

Tissues and cell types examined:
bone marrow
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION:
dose selection: on basis of the results from a pre-experiment.

TREATMENT:
10 animals per group were evaluated for micronuclei. At least 2000 polychromatic erythrocytes (PCE) per animal were scored. Cytotoxicity was evaluated by the ratio of polychromatic to normochromatic erythrocytes (determined in the same samples as used for micronuclei scoring)




Evaluation criteria:
A test substance is classified as mutagenic if it induces either a dose-related increase in
the number of micronucleated polychromatic erythrocytes, which clearly exceeds the
negative control range or a relevant positive response for at least one of the test points.
Statistical methods (nonparametric Mann-Whitney test (8)) can be used as an aid in
evaluating the results. However, the primary point of consideration is the biological
relevance of the results.
A test substance producing neither a dose-related increase in the number of
micronucleated polychromatic erythrocytes nor a positive response at any of the test
points is considered non-mutagenic in this system.
Statistics:
A non-parametric Mann-Whitney-Test was performed.

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid

Any other information on results incl. tables

The study was undertaken to investigate the potential of
isobutyl acrylate to induce micronuclei in polychromatic
erythrocytes (PCE) in bone marrow of mice.

Isobutyl acrylate did not induce micronuclei at any dose
level or any harvesting time used in this study. Isobutyl
acrylate was considered non-clastogenic and non-aneugenic in
this assay.

The mean number of normochromatic erythrocytes was not
increased after treatment with the test substance as
compared to the controls, indicating that isobutyl acrylate
had no cytotoxic effect on the bone marrow.

The positive control substance induced a distinct increase
of micronuclei.

Clinical signs of toxicity:
males at 1000 mg/kg bw: reduced spontaneous activity, eyelid
closure, apathy, prostrate position.
females at 1250 mg/kg bw: reduced spontaneous activity,
eyelid closure, apathy, prostrate position.

In the dose range-finder pre-experiment, 1250 mg/kg bw i.p.
were lethal to both tested male animals. 1000 mg/kg bw
induced clear signs of toxicity in 7 male animals (reduced
activity, eyelid closure, apathy, prostrate position). In
females, 1500 mg/kg bw i.p. were lethal for 1 of 2 animals.
At 1250 mg/kg bw clear signs of toxicity were observed in 7
female animals (reduced activity, eyelid closure, apathy,
prostrate position).

Summary of Micronucleus Test Results

Males

Test group

dose (mg/kg bw)

sampling time (h)

PCEs with micronuclei (‰)

range

PCE / NCE

vehicle

0

24

1.20

2 - 3

2000 / 1965

test substance

250

24

0.60

0 - 3

2000 / 1888

test substance

500

24

0.60

0 - 3

2000 / 2141

test substance

1000

24

1.20

1 - 4

2000 / 2371

positive control

40

24

14.90

17 - 36

2000 / 1771

vehicle

0

48

0.00

0 - 0

2000 / 2022

test substance

1000

48

0.40

0 - 2

2000 / 2642


Females:

Test group

dose (mg/kg bw)

sampling time (h)

PCEs with micronuclei (‰)

range

PCE / NCE

vehicle

0

24

0.10

0 - 1

2000 / 1965

test substance

312.5

24

0.50

0 - 3

2000 / 1888

test substance

625

24

0.40

0 - 3

2000 / 2141

test substance

1250

24

0.20

0 - 2

2000 / 2371

positive control

40

24

12.10

11 - 43

2000 / 1771

vehicle

0

48

0.00

0 - 0

2000 / 2022

test substance

1250

48

0.10

0 - 21

2000 / 2642

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative