3-Isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate homopolymer, isocyanurate type

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Remarks:

Type of genotoxicity: chromosome aberration

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2006-09-09-2007-01-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study; GLP study without deviations

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2007

Report date:

2007

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Version / remarks:

(1997)

Deviations:

no

GLP compliance:

yes

Type of assay:

in vitro mammalian chromosome aberration test

Test material

Test material information

Constituent 1

Reference substance name:

Benzophenone-3,3':4,4'-tetracarboxylic dianhydride

EC Number:

219-348-1

EC Name:

Benzophenone-3,3':4,4'-tetracarboxylic dianhydride

Cas Number:

2421-28-5

Molecular formula:

C17H6O7

IUPAC Name:

5,5'-carbonylbis(2-benzofuran-1,3-dione)

Test material form:

solid

Details on test material:

Physical State: solid
Colour: amber
Purity: 97.2%

Method

Species / strain

Species / strain / cell type:

other: Chinese hamster ovary (CHO) cells

Details on mammalian cell type (if applicable):

Species/cell type: CHO cells as originally isolated by Kao and Puck  (1968), obtained from Prof. Dr. A.T. Natarajan (University of Leiden, 
The  Netherlands)

Additional strain / cell type characteristics:

not specified

Metabolic activation:

with and without

Metabolic activation system:

S9-mix based on liver homogenate fraction  from male Wistar rats, induced with Aroclor 1254 (i.p.)

Test concentrations with justification for top dose:

up to 100 mg/l, see below

Vehicle / solvent:

Vehicle: dimethyl sulfoxide (DMSO)

Controls

Controls 1

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

vehicle (DMSO)

True negative controls:

no

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

+S9-mix

Migrated to IUCLID6: 5 mg/l

Controls 2

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

vehicle (DMSO)

True negative controls:

no

Positive controls:

yes

Positive control substance:

mitomycin C

Remarks:

-S9-mix

Migrated to IUCLID6: Test 1: 0.1 mg/l; Test 2: 0.05 mg/l

Details on test system and experimental conditions:

- No. of metaphases analyzed: 100/culture = 200/concentration. At least  500 nuclei/slide examined for mitotic index

ADMINISTRATION: 
- Dosing:  
Stock solution (50 or 10 g/l) in vehicle dimethyl sulfoxide (DMSO).   
Solubility test: 1; 2; 3.9; 7.8; 15.6; 31.3; 62.5; 125; 250; 500 mg/l   
Test 1: 0.1; 0.2; 0.39; 0.78; 1.56; 3.13; 6.25; 12.5; 25; 50; 75; 100  mg/l   
Selected for sampling: 6.25; 12.5; 25; 50; 75; 100 mg/l   
Test 2: 30; 40; 50; 60; 80; 100 mg/l, all sampled. 2.5; 5; 10; 20 mg/l  only -S9, not sampled.   
Both for presence and absence of S9-mix, 3 relevant concentration levels per test were analyzed for chromosomal aberrations. The highest  level 
selected should have reduced the mitotic index by 50-70 %.
- Number of replicates: 2
- Application:    
Test 1: after 4 hours exposure visual inspection; replace medium with  test substance by medium without test substance;  
12 hours later (i.e. at 16 hours) visual inspection, addition of  colcemid (resulting concentration 0.1 mg/l);   
at 18 hours harvest   
Test 2: similar to Test 1, except continuos exposure for 18 hours (i.e.  no replacement of medium) of samples without S9-mix 
- Positive and negative control groups and treatment:    
negative: vehicle (DMSO)   
positive (+S9): cyclophosphamide (5 mg/l)   
positive (-S9): mitomycin C (Test 1: 0.1 mg/l, Test 2: 0.05 mg/l)

Evaluation criteria:

The study is considered valid if:
(1) the positive controls show a significant increase in the number of aberrant cells and   
(2) the negative controls are within historical ranges.

A response is considered to be positive if:
a statistically significant increase in the number of aberrant cells is observed which is   
(1) either concentration-related   
(2) or reproduced in the second experiment at a similar dose level.

A response is considered to be equivocal if:
0.05

Statistics:

Fisher's exact probability test (two-sided) for significant differences between treated and control cultures

Results and discussion

Test results

Species / strain:

Chinese hamster Ovary (CHO)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

approx. 100 mg/l (-S9); > 100 mg/l (+S9)

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

In the first chromosomal aberration test, in both the absence and presence of a metabolic activation system, the test substance was weakly to
slightly toxic to the cells, at three concentrations analysed. In the second chromosomal aberration test, in the presence of S9-mix, the test
substance was not toxic to the cells at comparable dose levels. In the second chromosomal aberration test, in the absence of S9-mix, the test
substance was slightly toxic for the cells at two lowest concentrations analysed and clearly toxic at the highest concentration analysed.
Both chromosomal aberration tests did not induce a statistically significant increase in the number of aberrant cells, when compared to the
number of aberrant cells found in the negative (DMSO) control cultures.

Remarks on result:

other: other: Chinese hamster Ovary (CHO)

Remarks:

Migrated from field 'Test system'.

Any other information on results incl. tables

RESULT:

PRECIPITATION CONCENTRATION: 30 mg/l and higher
-------------------------------------------
MITOTIC INDEX AND CHROMOSOMAL ABERRATIONS (excl. gaps): 
-------------------------------------------
Concentration        % M.I.         % C.A.
-------------------------------------------
- Test 1, with S9
  neg. control        100            1.5
  100 mg/l             83            0.5
   75 mg/l             98            0.0
   50 mg/l             87            1.0
   25 mg/l            117       not inspected
  pos. control         38           29.5 ***
-------------------------------------------
- Test 1, without S9
  neg. control        100            0.0
  100 mg/l             91            0.0
   75 mg/l             97            0.0
   50 mg/l             78            0.0
   25 mg/l            111       not inspected
  pos. control        100           26.5 ***
-------------------------------------------
- Test 2, with S9
  neg. control        100            0.0
  100 mg/l            110            1.0
   80 mg/l            118            1.0
   60 mg/l            108       not inspected
   30 mg/l            127            1.0
  pos. control         51           39.5 ***
-------------------------------------------
- Test 2, without S9
  neg. control        100            0.0
  100 mg/l             53            0.5
   80 mg/l             73            0.0
   60 mg/l             92       not inspected
   30 mg/l             86            1.0
  pos. control         77           42.0 ***-
-------------------------------------------
*** p<=0.001 / ** p<=0.01 / * p<=0.05
-------------------------------------------
CYTOTOXIC CONCENTRATION: 
- With metabolic activation: > 100 mg/l
- Without metabolic activation: approx. 100 mg/l

Applicant's summary and conclusion

Conclusions:

In both the first and second chromosomal aberration test, the test substance IPDI homopolymer did not induce a statistically significant increase in
the number of aberrant cells, at any of the concentrations and treatment periods analysed, when compared to the number of aberrant cells found in
the vehicle (DMSO) control cultures. Thus, under the conditions used in this study, IPDI homopolymer was not clastogenic for CHO cells.

Executive summary:

The test substance IPDI homopolymer was examined for its potential to induce structural chromosomal aberrations in Chinese Hamster Ovary (CHO) cells, in both the absence and presence of a metabolic activation system (S9 -mix). The study was carried out according to OECD method no. 473 in compliance with the current OECD Principles of Good Laboratory Practice. Dimethylsulfoxide (DMSO) was used as vehicle for the test substance. Two separate chromosomal aberration tests were conducted. In all instances, duplicate cultures were used. The highest concentration tested was based on solubility of the test substance.

In both the first and second chromosomal aberration test, the test substance IPDI homopolymer did not induce a statistically significant increase in the number of aberrant cells, at any of the concentrations and treatment periods analysed, when compared to the number of aberrant cells found in the vehicle (DMSO) control cultures.

The data obtained support the conclusion that, under the conditions used in this study, the test substance IPDI homopolymer was not clastogenic for Chinese Hamster Ovary (CHO) cells.