Methylthiouracil

Eye irritation

Administrative data

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Materials and methods

Test guideline

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)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Methylthiouracil

EC Number:

200-252-3

EC Name:

Methylthiouracil

Cas Number:

56-04-2

Molecular formula:

C5H6N2OS

IUPAC Name:

methylthiouracil

Test material form:

solid: crystalline

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Korde Chemicals Pvt. Ltd. / 151117
- Expiration date of the lot/batch: 14.11.2019
- Purity test date: 15.11.2017

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Ambient temperature
- Stability under test conditions: stable
- Solubility and stability of the test substance in the solvent/vehicle: not specified
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: not specified

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing:
- Final preparation of a solid:

Test animals / tissue source

Species:

cattle

Details on test animals or tissues and environmental conditions:

SOURCE OF COLLECTED EYES
- Source: Local abattoir (Slaughter house), Near Frazer town, Bengaluru
- Number of animals:
- Characteristics of donor animals (e.g. age, sex, weight):
- Storage, temperature and transport conditions of ocular tissue (e.g. transport time, transport media and temperature, and other conditions):
- Time interval prior to initiating testing:
- indication of any existing defects or lesions in ocular tissue samples:
- Indication of any antibiotics used:

Test system

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

100 mg

Duration of treatment / exposure:

4 h

Details on study design:

SELECTION AND PREPARATION OF CORNEAS

QUALITY CHECK OF THE ISOLATED CORNEAS

NUMBER OF REPLICATES

NEGATIVE CONTROL USED

SOLVENT CONTROL USED (if applicable)

POSITIVE CONTROL USED

APPLICATION DOSE AND EXPOSURE TIME

TREATMENT METHOD: [closed chamber / open chamber]

POST-INCUBATION PERIOD: yes/no. If YES please specify duration

REMOVAL OF TEST SUBSTANCE
- Number of washing steps after exposure period:
- POST-EXPOSURE INCUBATION:

METHODS FOR MEASURED ENDPOINTS:
- Corneal opacity:
- Corneal permeability: passage of sodium fluorescein dye measured with the aid of [UV/VIS spectrophotometry / microtiter plate reader] (OD490)
- Others (e.g, pertinent visual observations, histopathology): (please specify)

SCORING SYSTEM: In Vitro Irritancy Score (IVIS)

DECISION CRITERIA: please specify if the decision criteria as indicated in the TG was used.

Results and discussion

In vitro

Results

Irritation parameter:

in vitro irritation score

Value:

6.699

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Any other information on results incl. tables

Table 1. Opacity calculations of negative control.

Cornea nro.	Blank value Io (lux)	Pretreatment cornea reading I (lux)	Initial opacity	Post-treatment cornea reading I (lux)	Final opacity	Change of opacity	Corrected opacity	Mean opacity
4	502	455	5	450	5	0	na	1
5	502	449	5	435	7	2	na	1
6	502	497	1	480	2	1	na	1

Table 2 . Opacity calculations of positive control.

Cornea nro.	Blank value Io (lux)	Pretreatment cornea reading I (lux)	Initial opacity	Post-treatment cornea reading I (lux)	Final opacity	Change of opacity	Corrected opacity	Mean opacity
27	502	453	5	123	123	118	117	162,67
28	502	442	6	80	211	205	204	162,67
29	502	454	5	94	173	168	167	162,67

Table 3. Opacity calculations of test item, methylthiouracil.

Cornea nro.	Blank value Io (lux)	Pretreatment cornea reading I (lux)	Initial opacity	Post-treatment cornea reading I (lux)	Final opacity	Change of opacity	Corrected opacity	Mean opacity
4	502	455	5	450	5	0	na	1
5	502	449	5	435	7	2	na	1
6	502	497	1	480	2	1	na	1

Applicant's summary and conclusion

Interpretation of results:

study cannot be used for classification

Conclusions:

In conclusion, the test item 6-Methyl-2-Thiouracil cannot be predicted as not classified for eye irritation/serious eye damage or as causing serious eye damage with the BCOP test method.

Executive summary:

The evaluation of the occular irritancy of methylthiouracil was carried out using the bovine corneal opacity and permeability assay (BCOP). 100 mg of test item was applied undiluted on the corneal surface by open chamber method. The IVIS scores were as follows: negative control (distilled water) 1.228, positive control (chlorhexidine) 163.377 and test item 6.699. The test item was classified as no prediction can be made based on UN GHS criteria.