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Toxicological information

Genetic toxicity: in vivo

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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:
11-14 September, 1989
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: According to GLP and OCED 474, conducted on two surrogates which have comparable composition

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1989
Report Date:
1989

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
Deviations:
no
Principles of method if other than guideline:
The test was performed according to OECD 474.
GLP compliance:
yes
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
The test material was identified by the following information: "Gistex Standard Powder, Autolyzed yeast extract. FM 8850-03. 20-6-1989".

Test animals

Species:
mouse
Strain:
Swiss
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Wiga GmbH, Sulzfeld, F.R. Germany.
- Age at study initiation: young adult
- Weight at study initiation: mean weight in range 30.7-31.8 g (M) or 23.9-25.8 g (F)
- Assigned to test groups randomly: yes
- Fasting period before study: no
- Housing: males individually and females 5/cage
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum):ad libitum
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22±1°C
- Humidity (%): 57-82%
- Air changes (per hr): 10/hour
- Photoperiod (hrs dark / hrs light): 12 h light and 12 h dark

IN-LIFE DATES: From 11-14 September, 1989

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
- Vehicle(s)/solvent(s) used: water
- Justification for choice of solvent/vehicle: not provided but from other studies it appeared that the test material is soluble in water.
- Concentration of test material in vehicle: 20% w/v
- Amount of vehicle (if gavage or dermal): 10 mL/kg bw
- Type and concentration of dispersant aid (if powder): not relevant
- Lot/batch no. (if required): not relevant
- Purity: no data
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: the solutions were prepared just prior to use.
Duration of treatment / exposure:
Single oral dose to 15 animals/sex (6 animals/sex for positive control); 5 animals/sex (2 animals/sex for positive control) were sacrificed for bone marrow collection at 24, 48 and 72 hours post-dose.
Frequency of treatment:
Single oral dose.
Post exposure period:
not relevant
Doses / concentrations
Remarks:
Doses / Concentrations:
2000 mg/kg bw
Basis:
actual ingested
No. of animals per sex per dose:
15 animals/sex for Gistex treatment and vehicle control, 6 animals/sex for positive control; this provided for 5 animals/sex (2 animals/sex for positive control) for bone marrow collection at 24, 48 and 72 hours post-dose.
Control animals:
yes, concurrent vehicle
Positive control(s):
mitomycin C
- Justification for choice of positive control(s): recommended by OECD 474
- Route of administration: intraperitoneal
- Doses / concentrations: 1.5 mg/kg bw

Examinations

Tissues and cell types examined:
bone marrow from dissection of femur
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION: highest dose recommended by OECD 474

TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields):see above

DETAILS OF SLIDE PREPARATION: Glass-drawn smears of bone marrow were prepared (two smears per animals).

METHOD OF ANALYSIS: The incidence of MPE (micronucleated polychromatic erythrocytes) and MNE (micronucleated normochromatic erythrocytes) and the total numbers of PE (polychromatic erythrocytes) and NE (normochromatic erythrocytes) were recorded in a total of at least 2000 and maximally 3000 E (erythrocytes) per animal, in such a way that a minimum of 1000 E was observed, if feasible.

OTHER:
Evaluation criteria:
None reported.
Statistics:
In the first step, the fraction of MPE, MNE and ME per counted numer of PE, NE and E, respectively, were analysde with a generalized linear model using a binomial error-distribution, and the numbers of PE per 1000 E were analyzed with linear regression techniques. As a second stage, a posteriori comparisons of treatment groups with negative controls were carried out with asymptotic t-tests if either the main effect of treatment or the treatment by sex interaction was significant.

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
no effects
Vehicle controls validity:
valid
Negative controls validity:
not examined
Positive controls validity:
valid
Additional information on results:
No signs of intoxiciation were observed. Mean body weigths of test and control anaimals were comparable in males and females.
For results of microscopic evalaution see tables below.
The incidence of MPE, MNE and ME per 1000 PE, NE and E, respectively were comparable between controls and test animals at all harvest times. The positive control gave the expected response.

PE counts per 1000 E were statistically different after 48 hours in males and females treated with Gistex. This finding is considered to be of doubtful toxicological significance as there was no consistent trend in time, and as there were opposite changes in males and females. The report also stated that all values were within the range normally seen in controls, but historical control data to verify this statement were not presented in the report.

Any other information on results incl. tables

Table 1. Group mean numbers of micronucleated erythrocytes per 1000 PE, 1000 NE and 1000 E.

dose

males

females

parameter

treatment

/kg bw

24 h

48 h

72 h

24 h

48 h

72 h

mean number of MPE/1000 PE

water

10 mL

0.3

1

0.8

0.6

0.7

1

Gistex

2000 mg

0.9

0.9

0.6

1.1

0.8

0.4

MC

1.5 mg

50.4***

12.0**

1.2

25.0***

14.6***

3.8

mean number of MNE/1000 NE

water

10 mL

0.7

0.6

0.6

0.6

1.5

0.9

Gistex

2000 mg

0.8

0.7

0.7

1

0.7

0.9

MC

1.5 mg

6.5***

4.6***

0

2.4*

7.1***

2.3

mean number of ME/1000E

water

10 mL

0.5

0.8

0.7

0.6

1.1

1

Gistex

2000 mg

0.9

0.8

0.6

1.1

0.8

0.6

MC

1.5 mg

20.3***

5.6***

0.2

11.2***

8.8***

2.7*

* p<0.05; ** p<0.01; *** p<0.001

PE = polychromatic erythrocytes

NE = normochromatic erythrocytes

E = erythrocytes (PE + NE)

MPE, MNE, ME = micronucleated PE, NE, E, respectively

MC = mitomycin C

Table 2. Group mean numbers of PE per 1000 E.

dose

males

females

parameter

treatment

/kg bw

24 h

48 h

72 h

24 h

48 h

72 h

mean number of PE/1000 E

water

10 mL

572

428

518

470

555

436

Gistex

2000 mg

519

564***

513

534

455*

462

MC

1.5 mg

319***

156***

198***

430

236***

258***

* p<0.05; ** p<0.01; *** p<0.001

PE = polychromatic erythrocytes

E = erythrocytes

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
In a mouse micronucleus test conducted at a single oral dose dose of 2000 mg/kg bw (harvest times 24, 48 and 72 hours post-dose), the test substance was negative.