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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:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
not indicated
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Read-across from a substance that is less bioavailable than Barium Chromate. Publication with unknown GLP study status and limited details. However the test is similar to guideline OECD 474 / EC B.12 and its sensitivity is validated by the positive result obtained.

Data source

Reference
Reference Type:
publication
Title:
In Vivo Clastogenicity of Lead Chromate in Mice
Author:
Watanabe M, Takayama Y, Koike M et al
Year:
1985
Bibliographic source:
Tohoku J Exp Med. 1985 Jul;146(3):373-4
Report date:
1985

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
No details
GLP compliance:
not specified
Type of assay:
micronucleus assay

Test material

Constituent 1
Reference substance name:
Lead chromate
IUPAC Name:
Lead chromate
Details on test material:
- Name of test material (as cited in study report): lead chromate
- Molecular formula (if other than submission substance): PbCrO4
- Analytical purity: 92%

- No other details available

- Surrogate PbCrO4 is used, instead of proposing a new test on the registered substance (with 15% of BaCrO4, source of CrVI) because:
. both BaCrO4 and PbCrO4 contain the chromate ion (CrO4--) which is the source of CrVI (mutagen and carcinogen)
. MW of BaCrO4 and PbCrO4 are close: 253 and 323
. water solubilities of BaCrO4 and PbCrO4 are both at lowest end of all chromates: 4.4 mg/L (28°C)* and 0.58 mg/L (25°C)*
. compared MW and water solubility indicate that BaCrO4 should be a bit more bioavailable than PbCrO4, so that any positive result with the latter can be extrapolated to BaCrO4 and therefore to the registered substance
* Source of solubility data: Scientific Basis for Swedish Occupational Standards XXI. Criteria Group for Occupational Standards. Ed. Johan Montelius, National Institute for Working Life, S-112 79 Stockholm, Sweden. ISBN 91-7045-582-1, 2000.

Test animals

Species:
mouse
Strain:
C57BL
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS
ENVIRONMENTAL CONDITIONS
IN-LIFE DATES:
all no data reported

Administration / exposure

Route of administration:
intraperitoneal
Vehicle:
- Vehicle(s)/solvent(s) used: 0.5% gum arabic saline

- no other data reported
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
suspended in 0.5% gum arabic saline, which had been milliporefiltered. The chemical of 0.8 ml solution was administered i.p.
Duration of treatment / exposure:
twice at a 24 hr-interval
Frequency of treatment:
twice at a 24 hr-interval
Post exposure period:
Examined 24h after 2nd administration
Doses / concentrations
Remarks:
Doses / Concentrations:
0.5, 1, 2 and 4 g/kg
Basis:
other: PbCrO4 injected levels
No. of animals per sex per dose:
10 males
Control animals:
yes, concurrent vehicle
Positive control(s):
none (but test validated by positive result with test item)

Examinations

Tissues and cell types examined:
Bone marrow polychromatic and normochromatic erythrocytes
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION: not indicated

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

DETAILS OF SLIDE PREPARATION:
The mouse was killed by cervical dislocation and the femoral bone marrow submerged in calf serum was pushed off onto a glass slide to prepare the smear. After methanol fixation, the smears were stained by May-Grünwald and Giemsa solutions.

METHOD OF ANALYSIS:
Scoring micronucleated cells in 1000 each of polychromatocytes and normochromocytes and the ratio of polychromatocytes to normochromocytes (P/N ratio) on the slide was determined.
Evaluation criteria:
not indicated
Statistics:
Welch test and t-test vs. control

Results and discussion

Test results
Sex:
male
Genotoxicity:
positive
Remarks:
from 1 g/kg
Toxicity:
yes
Remarks:
from 0.5 g/kg
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
not applicable
Additional information on results:
RESULTS OF RANGE-FINDING STUDY
- no details published

RESULTS OF DEFINITIVE STUDY

- Induction of micronuclei (for Micronucleus assay): % in polychromatocytes: 0.63, 1.01, 1.58, 1.44 and 1.95 at 0, 0.5, 1, 2 and 4 g/kg
no micronucleus induction in normochromatocytes.

- Ratio of PCE/NCE (for Micronucleus assay): 0.81, 0.34, 0.25, 0.16 and 0.08 at 0, 0.5, 1, 2 and 4 g/kg

- Appropriateness of dose levels and route:
Dose-levels: excessive myelotoxicity (i.e. ratio PCE/(PCE+NCE) less than 20% of controls) occured only at the top-dose, so control and three test item doses stay interpretable.
The appropriate route would be inhalative (a systemic availability of barium chromate has been demonstrated after inhalation),* but no validated or guideline-compliant assay exists for this route and the target tissue should not be bone marrow (too far from entry site). Otherwise, based on guideline EC B.12 / OECD 474, oral route can be excluded due to poor absorption.* Therefore intraperitoneal administration is the only appropriate route for exposure to the bone marrow.
*: see toxicokinetics under 7.1

- Statistical evaluation: doses indicated in previous paragraph are those with p<0.01 significant effect

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): positive
These results strongly suggest that PbCrO4 administered i.p. to mice gives rise to chromosome damage (as shown by micronucleus induction) in bone marrow and suppressed hematopoiesis (as shown by decreased PCE/NCE ratio).

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