Registration Dossier

Toxicological information

Genetic toxicity: in vivo

Currently viewing:

Administrative data

Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Remarks:
Type of genotoxicity: chromosome aberration
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
not reported.
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in accordance with generally accepted scientific principles. Justification of read-across: Dioctyltin bis (IOMA) and dioctyltinnbis (2-EHMA) are isomers of the same compound and are expected to be chemically and toxicologically equivalent.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1980
Report Date:
1980

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)
Deviations:
no
Principles of method if other than guideline:
A preliminary toxicity study was conducted to obtain suitable dose levels for the micronucleus test. In the micronucleus test the test material was prepared in 1% methylcellulose and administered by oral gavage to 25 male and 25 female CFLP strain mice. The test material was administed in 2 equal administrations separated by an interval of 24 hours. Following the second dose the animals were observed for a further 6 hours before being sacrificed and samples of the femur bone marrow taken. The bone marrow smear was plated onto a microscope slide and prepard for examination, the incidence of micronucleated cells per 2000 polychromatic and 2000 normochromatic to polychromatic erythrocytes was determined for each animal.
GLP compliance:
not specified
Type of assay:
micronucleus assay

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Test item: ZK 30434, Dioctyltin bis(IOMA) [CAS No. 26401-97-8]:Octyltin tris(IOMA) [CAS No.26401-86-5] (80:20% mixture)
Physical properties: colourless liquid
Lot number: RU 20/77

Test animals

Species:
mouse
Strain:
other: CFLP
Sex:
male/female
Details on test animals and environmental conditions:
Breeder: Anglia Laboratory, Alconbury, Huntingdon, UK
Initial body weights: 19-23 g
Acclimitisation: one week
Housed in plastic disposable cage (5/cage)
Environmental conditions: maintained at 21 ± 2 ºC and 50 ± 5% relative humidity with 20 changes of air/hour
Photoperiod: illuminated by artificial light for 12 hours per day
Diet: Grain Harvester Anglia Lab animal diet and tap water ad libitum
Fasted overnight before treatment
Mice (CFLP) were pretested to determine target dose for micronucleus test.

Administration / exposure

Route of administration:
oral: gavage
Vehicle:
1% methylcellulose (also used as negative control)
Details on exposure:
Total dose (in 2 administrations) were 2250, 4500, 1900 mg/kg; positive control mitomycin C = 14 mg/kg

EXPERIMENTAL DESIGN
Group Material Conc mg/mL Dose mL/10g Dose mg/kg Total (mg/kg) M F
1 control (veh) - 0.1 - - 5 5
5 ZK 30434 112.5 0.1 1125 2250 5 5
6 ZK 30434 225 0.1 2250 4500 5 5
7 ZK 30434 450 0.1 4500 9000 5 5
8 control (pos) 0.7 0.1 7 14 5 5
Duration of treatment / exposure:
30 hours (doses at 0 and 24 hours, sacrifice 6 hours after last dose)
Frequency of treatment:
2 doses separated by an interval of 24 hours.
Post exposure period:
6 hours
Doses / concentrations
Remarks:
Doses / Concentrations:
2250, 4500, and 9000 mg/kg bw
Basis:
actual ingested
No. of animals per sex per dose:
5/sex/dose (10)
Control animals:
yes, concurrent vehicle
Positive control(s):
Mitomycin C in physiological saline by IP injection of 14 mg/kg (total of 2 doses)

Examinations

Tissues and cell types examined:
Animals were sacrificed at 6 hours after the last dose by cervical dislocation. Femurs were dissected out from each animal, cleared of tissue and one epiphysis removed from each bone
Details of tissue and slide preparation:
A direct bone marrow smear (from epiphysis from each femur) was made and placed on a methanol-cleaned slide. Smears were air dried and fixed in methanol overnight. After fixation the smears were air-dried and placed in buffered distilled water (pH 6.8) for 10 minutes prior to staining in Giemsa (dilution factor, 1 part Giemsa:9 parts buffered distilled water) for 10 minutes. After rinsing in buffered water, slides were air-dried, then defatted in xylene for 10 minutes and mounting in DPX. Stained smears were examined by light microscopy.
Evaluation criteria:
Incidence of micronucleated cells per 2000 polychromatic and 2000 normochromatic ertyhrocytes per animal was deterimned for each animal.
Statistics:
Ratios were analyzed by Barlett's test < 0.001 using non-paraetric methods based on Kruskal-Wallis mean ranks. These methods are more than robust against inequality of variance than classical variance methods. Postive control groups dosed with mitomycin C and the groups dosed with ZK 30 434 were compared to vehicle control using the non-parametric equivalent of the least significant differences.

Results and discussion

Test results
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes
Remarks:
bone marrow depression
Vehicle controls validity:
valid
Negative controls validity:
not examined
Positive controls validity:
valid

Any other information on results incl. tables

Under the conditions studied, ZK 30 434 failed to show any evidence of mutagenic potential when administered orally in this test procedure. However, evidence of bone marrow depression was observed.

Group mean number of micronucelaetd cells per 2000 normochromatic erythrocytes and 2000 polychromatic erythrocytes per animal and the group mean ratio.

    Normochromatic (N) Polychromatic (P) Ratio N:P erythrocytes
Material Total dose (mg/kg) Mean Range Mean Range Mean  Range
Vehicle control - 2.2 0-6 2.8 1-6 1.09 0.93-1.22
ZK 30 434 2250 2.3 0-6 2.5 0-5 1.38 1.19-1.69
ZK 30 434 4500 2.4 0-5 2.4 0-6 1.72** 1.47-2.09
ZK 30 434 9000 2.3 0-6 2.6 1-5 3.93*** 2.56-5.39
Positive control 14 11.4*** 8-15 89.5*** 74-115 10.46*** 7.75-15.38

** p<0.01

*** p< 0.001

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): negative
Under the conditions studied, ZK30434 failed to show any evidence of mutagenic potential when administered orally in this test procedure.
However, evidence of bone marrow depression was observed, which is an indication that the test item reached the bone marrow.
Executive summary:

The effect of ZK 30 434 on the incidence of micronucleated polychromatic erythrocytes from the bone marrow of mice was tested with doses of 2250, 4500, and 9000 mg/kg bodyweight administered by oral gavage in two equal doses separated by an interval of 24 hours. Negative control (1% methycellulose by oral gavage) and postive control group (14 mg/kg mitomycin C by injection) were run concurrently. After 6 hours of the second dose bone marrow smears were examined for the presence of micronuclei in 2000 polychromatic and 2000 normochromatic erythorcytes per mouse.

At all doses of ZK 30 434 both the group mean micronucleated cell counts were comparable with the concurrent control values. The ratio of normochromatic to polychromatic cells was comparable to controls for 2250 mg/kg group and significantly higher for 4500 and 9000 mg/kg groups (by Kruskal-Wallis method). Postive control produced expected increase in micronucleated cell count and ratio. It was concluded that ZK 30 434 failed to show any evidence of mutagenic potential when adminsitered orally in the test procedure. However, evidence of bone marrow depression was observed, which is an indication that the test item reached the bone marrow.