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Toxicological information

Eye irritation

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Administrative data

Endpoint:
eye irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2015-06-01 to 2015-06-11
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2015
Report date:
2015

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU method B.47 (Bovine corneal opacity and permeability test method for identifying ocular corrosives and severe irritants)
Deviations:
no
Principles of method if other than guideline:
The study procedures described in the study are also in compliance with the following documents:
- The Ocular Toxicity Working Group (OTWG) of the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) and the National Interagency Centre for the Evaluation of Alternative Toxicological Methods (NICEATM), Background Review Document (BRD): current status of in vitro test methods for identifying ocular corrosives and severe irritants: The Bovine Corneal Opacity and Permeability (BCOP) Test Method, March 2006.
- In Vitro Techniques in Toxicology Database (INVITTOX) protocol 127. Bovine Opacity and Permeability (BCOP) Assay, 2006.
- Gautheron P, Dukic M, Alix D and Sina J F, Bovine corneal opacity and permeability test: An in vitro assay of ocular irritancy. Fundam Appl Toxicol 18:442-449, 1992.
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
9-hydroxy-3-(2-hydroxyethyl)-2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one
EC Number:
605-935-3
Cas Number:
181525-38-2
Molecular formula:
C11H12N2O3
IUPAC Name:
9-hydroxy-3-(2-hydroxyethyl)-2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one
Test material form:
solid: particulate/powder
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: I14FB2740
- Expiration date of the lot/batch: 2016-06-26 (retest date)
- Purity test date: 2014-07-11

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature
- Stability under test conditions: no data
- Solubility and stability of the test substance in the solvent/vehicle: no data
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: no data

FORM AS APPLIED IN THE TEST (if different from that of starting material)
first test = pure (light yellow powder) / second test = 20% thick white suspension prepared in physiological saline

Test animals / tissue source

Species:
cattle
Strain:
other: not applicable
Details on test animals or tissues and environmental conditions:
TEST ANIMALS
- Source: bovine eyes from young cattle were obtained from the slaughterhouse (Vitelco, 's Hertogenbosch, The Netherlands), where the eyes were excised by a slaughterhouse employee as soon as possible after slaughter. The eyes were used as soon as possible but within 4 hours after slaughter. Eyes were collected and transported in physiological saline in a suitable container under cooled conditions.

- Preparation of corneas: The eyes were checked for unacceptable defects, such as opacity, scratches, pigmentation and neovascularization by removing them from the physiological saline and holding them in the light. Those exhibiting defects were discarded.
The isolated corneas were stored in a petri dish with cMEM (Eagle’s Minimum Essential Medium (Life Technologies, Bleiswijk, The Netherlands) containing 1% (v/v) L-glutamine (Life Technologies) and 1% (v/v) Foetal Bovine Serum (Life Technologies)). The isolated corneas were mounted in a corneal holder (one cornea per holder) of MC2 (Clermont-Ferrand, France) with the endothelial side against the O-ring of the posterior half of the holder. The anterior half of the holder was positioned on top of the cornea and tightened with screws. The compartments of the corneal holder were filled with cMEM of 32 ± 1°C. The corneas were incubated for the minimum of 1 hour at 32 ± 1°C.

- Cornea selection and opacity reading: after the incubation period, the medium was removed from both compartments and replaced with fresh cMEM. Opacity determinations were performed on each of the corneas using an opacitometer (OP-KIT, MC2, Clermont-Ferrand, France). The opacity of each cornea was read against an air filled chamber, and the initial opacity reading thus determined was recorded. Corneas that had an initial opacity reading higher than 3 were not used. Three corneas were selected at random for each treatment group.

Test system

Vehicle:
physiological saline
Controls:
yes, concurrent positive control
yes, concurrent negative control
Amount / concentration applied:
TEST MATERIAL
- Amount(s) applied (volume or weight with unit) in first test: 307.4 to 355.1 mg, applied directly on the corneas in such a way that the cornea was completely covered
- Amount(s) applied (volume or weight with unit) in second test: an excessive amount of the 20% (w/w) test item

NEGATIVE CONTROL:
- Amount(s) applied (volume or weight with unit): 750 µl
- Purity: no data

POSITIVE CONTROL:
- Amount(s) applied (volume or weight with unit): 750 µl
- Concentration: 20% (w/v)
- Purity: no data
Duration of treatment / exposure:
Corneas were incubated in a horizontal position for 240 ± 10 minutes at 32 ± 1°C.
Duration of post- treatment incubation (in vitro):
After 240 ± 10 minutes of treatment, opacity was measured with an opacitometer. The permeability measurement of the corneas was performed after the incubation period of 90 minutes ± 5 minutes following
the opacity measurement.
Number of animals or in vitro replicates:
3 eyes per group; 3 groups
Details on study design:
TREATMENT METHOD
- In the first test, the medium from the anterior compartment was removed and 750 μl of the negative control and 20% (w/v) Imidazole solution (positive control) were introduced onto the epithelium of the cornea. the test item was weighed in a bottle and applied directly on the corneas in such a way that the cornea was completely covered.
- In the second test which was requested by the sponsor, the medium from the anterior compartment was removed and 750 μl of either the negative control, positive control (20% (w/v) Imidazole solution) or an excessive amount of the 20% (w/w) test item was introduced onto the epithelium of the cornea.
The holder was slightly rotated, with the corneas maintained in a horizontal position, to ensure uniform distribution of the solutions over the entire cornea. Corneas were incubated in a horizontal position for 240 ± 10 minutes at 32 ± 1°C.

REMOVAL OF TEST SUBSTANCE
After the incubation the solutions and the test compound were removed and the epithelium was washed at least three times with MEM with phenol red (Eagle’s Minimum Essential Medium Life Technologies). Possible pH effects of the test item on the corneas were recorded. Each cornea was inspected visually for dissimilar opacity patterns. The medium in the posterior compartment was removed and both compartments were refilled with fresh cMEM and the opacity determinations were performed.

OPACITY MEASUREMENT
The opacitometer determined the difference in the light transmission between each control or treated cornea and an air filled chamber. The numerical opacity value (arbitrary unit) was displayed and recorded. The change in opacity for each individual cornea (including the negative control) was calculated by subtracting the initial opacity reading from the final post-treatment reading. The corrected opacity for each positive control or test item treated cornea was calculated by subtracting the average change in opacity of the negative control corneas from the change in opacity of each positive control or test item treated cornea.
The mean opacity value of each treatment group was calculated by averaging the corrected opacity values of the treated corneas for each treatment group.

APPLICATION OF SODIUM FLUORESCEIN
Following the final opacity measurement, permeability of the cornea to Na-fluorescein (Merck) was evaluated.

The medium of both compartments (anterior compartment first) was removed. The posterior compartment was refilled with fresh cMEM. The anterior compartment was filled with 1 ml of 5 mg Na-fluorescein/ml cMEM solution (Sigma-Aldrich Chemie GmbH, Germany). The holders were slightly rotated, with the corneas maintained in a horizontal position, to ensure uniform distribution of the sodium-fluorescein solution over the entire cornea. Corneas were incubated in a horizontal position for 90 ± 5 minutes at 32 ± 1°C.

PERMEABILITY DETERMINATIONS
After the incubation period, the medium in the posterior compartment of each holder was removed and placed into a sampling tube labelled according to holder number. 360 μl of the medium from each sampling tube was transferred to a 96-well plate. The optical density at 490 nm (OD490) of each sampling tube was measured in triplicate using a microplate reader (TECAN Infinite® M200 Pro Plate Reader). Any OD490 that was 1.500 or higher was diluted to bring the OD490 into the acceptable range (linearity up to OD490 of 1.500 was verified before the start of the experiment). OD490 values of less than 1.500 were used in the permeability calculation.

The mean OD490 for each treatment was calculated using cMEM corrected OD490 values. If a dilution was performed, the OD490 of each reading was corrected for the mean negative control OD490 before the dilution factor was applied to the readings.

INTERPRETATION:
The mean opacity and mean permeability values (OD490) were used for each treatment group to calculate an in vitro score:
In vitro irritancy score (IVIS) = mean opacity value + (15 x mean OD490 value)

Additionally the opacity and permeability values were evaluated independently to determine whether the test item induced irritation through only one of the two endpoints.

The IVIS cut-off values for identifying the test items as inducing serious eye damage (UN GHS Category 1) and test items not requiring classification for eye irritation or serious eye damage (UN GHS No Category) are given hereafter:
In vitro score range UN GHS
≤ 3 No Category
> 3; ≤ 55 No prediction can be made
>55 Category 1

Results and discussion

In vitro

Resultsopen allclose all
Irritation parameter:
in vitro irritation score
Run / experiment:
test item after 240 minutes of treatment (second test)
Value:
-0.6
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of irritation
Remarks:
IVIS range: -2.1 to 0.2
Irritation parameter:
cornea opacity score
Run / experiment:
test item after 240 minutes of treatment (second test)
Value:
-0.7
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
other: range = -2.0 to 0.0
Irritation parameter:
other: cornea permeability score
Run / experiment:
test item after 240 minutes of treatment (second test)
Value:
0.005
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
other: range: -0.006 to 0.016
Other effects / acceptance of results:
First test: The individual opacity scores for the negative controls ranged from 4 to 8, which is above the historical range, therefore the test was terminated.

Second test: The individual in vitro irritancy scores for the negative controls were 0.0. The individual positive control in vitro irritancy scores ranged from 116.2 to 156.2. Furthermore the opacity and permeability values of the positive control were within two standard deviations of the current historical mean. The corneas treated with the positive control were turbid after the 240 minutes of treatment.
The corneas treated with the test item showed opacity values ranging from -2.0 to 0.0 and permeability values ranging from -0.006 to 0.016. The corneas were clear after the 240 minutes of treatment with the test item. No pH effect of the test item was observed on the rinsing medium. Hence, the in vitro irritancy scores ranged from -2.1 to 0.2 after 240 minutes of treatment with the test item.

In the second test, the negative control responses for opacity and permeability were less than the upper limits of the laboratory historical range indicating that the negative control did not induce irritancy on the corneas. The mean in vitro irritancy score of the positive control (20% (w/v) Imidazole) was 133.6 (116.2 to 156.2) and within the historical positive control data range. It was therefore concluded that the test conditions were adequate and that the test system functioned properly.FIRST TEST: The individual opacity scores for the negative controls ranged from 4 to 8, which is above the historical range, therefore the test was terminated.

SECOND TEST:

Negative control:
- IVIS: 0.0 (same value for the 3 corneas)
- opacity score: 0.0 (same value for the 3 corneas)
- permeability score: 0.000 (-0.002 to 0.001)

Positive control:
- IVIS: 133.6 (116.2 to 156.2)
- opacity score: 104.3 (75.0 to 135.0)
- permeability score: 1.951 (1.412 to 2.746)

Other effects:
The corneas treated with the positive control were turbid after the 240 minutes of treatment.
The corneas were clear after the 240 minutes of treatment with the test item. No pH effect of the test item was observed on the rinsing medium.

Acceptance of results:
In the second test, the negative control responses for opacity and permeability were less than the upper limits of the laboratory historical range indicating that the negative control did not induce irritancy on the corneas. The mean in vitro irritancy score of the positive control (20% (w/v) Imidazole) was 133.6 (116.2 to 156.2) and within the historical positive control data range. It was therefore concluded that the test conditions were adequate and that the test system functioned properly.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
The test item did not induce ocular irritation through both endpoints, resulting in a mean in vitro irritancy score of -0.6 (-2.1 to 0.2) after 240 minutes of treatment.
Since the test item induced an IVIS ≤ 3, no classification is required for eye irritation or serious eye damage.