Saccharomyces cerevisiae, ext.

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:

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

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

Test material information

Constituent 1

Reference substance name:

Gistex standard powder, autolyzed yeast extract

IUPAC Name:

Gistex standard powder, autolyzed yeast extract

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 or test system 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.