6-amino-1,3-dimethyluracil

Endpoint summary

Description of key information

Skin sensitization in vivo: 10 (treatment) or 5 (control) female GOHI albino guinea pigs, guinea pig maximisation test, 10%intradermal induction, 50% epidermal induction, 25% challenge,OECD 406, GLP: not sensitizing

Skin sensitization in vivo: female CBA/CaOlaHsd mice, 4/dose, 5, 10, or 20% in DMSO, LLNA, OECD 429, GLP: not sensitizing

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Reference 1

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002-03-13 - 2002-04-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Version / remarks:

OECD Guidelines for Testing of Chemicals, Number 406 "Skin Sensitization", adopted by the Council on July 17,1992 (reported Paris, April 29,1993).

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Version / remarks:

Directive 96/54/EEC, B.6. "Acute Toxicity Skin Sensitization", July 30, 1996

Deviations:

no

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

Study was conducted prior to the implementation of REACH, and likely before the adoption of OECD TG 429 which was in the same year

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature at about 20 °C, away from direct sunlight
- Stability under test conditions: Stability in water: Max. 90 days

Species:

guinea pig

Strain:

other: Ibm: GOHI; SPF-quality guinea pigs (synonym: Himalayan spotted)

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: RCC Ltd, Biotechnology & Animal Breeding Division, Wölferstrasse 4, CH-4414 Füllinsdorf/Switzerland
- Females (if applicable) nulliparous and non-pregnant: yes
- Age at study initiation: 5 - 7 weeks
- Weight at study initiation: 396 - 432 g (pretest groups), 408 - 451 g (control and test groups)
- Housing: Individually in Makrolon type-4 cages with standard softwood bedding ("Lignocel", Schill AG, CH-4132 Muttenz) in Air-conditioned laboratory. Music was played during the daytime light period.
- Diet (e.g. ad libitum): Pelleted standard Provimi Kliba 3418, batch no. 116/01, guinea pig breeding / maintenance diet, containing Vitamin C (Provimi Kliba AG, CH-4303 Kaiseraugst), ad libitum.
- Water (e.g. ad libitum): Community tap water from Füllinsdorf, ad libitum.
- Acclimation period: One week for the control and test group under test conditions after health examination. No acclimatization for the animals of the pretest.
- Indication of any skin lesions: Only animals without any visible signs of illness were used for the study.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 ± 3 °C (target range)
- Humidity (%): 30-70%
Room temperature and humidity were monitored continuously and values outside of these ranges occasionally occurred, usually following room cleaning. These transient variations are considered not to have any influence on the study and, therefore, these data are not reported but are retained
- Air changes (per hr): 10-15
- Photoperiod (hrs dark / hrs light): The animals were provided with an automatically controlled light cycle of 12 hours light and 12 hours dark.
- IN-LIFE DATES:
From: 13-MAR-2002 (pretest) 20-MAR-2002 (main study)
To: 24-APR-2002

Route:

intradermal and epicutaneous

Vehicle:

water

Remarks:

purified

Concentration / amount:

10%, 0.1 ml (intrdermal)
50%, 0.2 ml (epicutaneous)

Day(s)/duration:

topical induction was made 1 week (day 8) after intradermal induction (day 1)

Adequacy of induction:

other: concentrations (intradermal) of 20 and 30% were not applicable

No.:

#1

Route:

epicutaneous, occlusive

Vehicle:

water

Remarks:

purified

Concentration / amount:

0.2 ml of a 25% solution

Day(s)/duration:

Two weeks after epidermal induction, day 22

Adequacy of challenge:

highest non-irritant concentration

No. of animals per dose:

10 (test group)
5 (control group)

Details on study design:

RANGE FINDING TESTS:
The test item concentrations described below were selected during a preliminary solubility testing which was performed before the study initiation date.
INTRADERMAL INJECTIONS:
Four intradermal injections (0.1 ml/site) of a 1:1 (v/v) mixture of Freund's Complete Adjuvant/physiological saline were made into the shaved neck of one guinea pig (no. 807). One week later one intradermal injection (0.1 ml/site) was made into the clipped flank of the same guinea pig at the concentration of C = 10 % of the test item in purified water. The concentrations of A = 30 % and B = 20 % were not applicable
Dermal reactions were assessed 24 hours later.
Based on the results, the test item concentration of 10 % was selected for intradermal induction in the main study.
EPIDERMAL APPLICATIONS:
Four intradermal injections (0.1 ml/site) of a 1:1 (v/v) mixture of Freund's Complete Adjuvant/physiological saline were made into the shaved neck of two guinea pigs. One week later both flanks of each of the guinea pigs were clipped and shaved just prior to the application. Thereafter 4 patches of filter paper (3x3 cm) were saturated with the test item at D = 50 % (technically the highest possible concentration to be applied sufficiently), E = 25 %, F = 15 % and G = 10 % in purified water and applied to the clipped and shaved flanks. The amount of test item preparation applied was approximately 0.2 g for the test item at 50 % and a volume of approximately 0.2 ml was applied for the remaining test item concentrations. The patches were covered by a strip of aluminum foil and firmly secured by elastic plaster wrapped around the trunk and covered with impervious adhesive tape. This procedure ensured the intensive contact of the test item. The dressings were removed after an exposure period of 24 hours.
Twenty-one hours after removal of the dressing the application site was depilated with an approved depilatory cream (VEET Cream, Reckitt & Colman AG, CH-4123 Allschwil) in order to visualize any restating erythema.
The depilatory cream was placed on the patch sites and surrounding areas, and left on for 3-5 minutes. It was then thoroughly washed off with a stream of warm, running water. Thereafter, the animals were dried with a disposable towel, and returned to their cages.
The reaction sites were assessed 24 and 48 hours after removal of the bandage for erythema and oedema according to the method of Magnusson and Kligman.
The allocation of the different test iem dilutions to the sites on the two animals was alternated in order to minimize site-to-site variation in responsiveness.
Based on the results obtained the concentration selected for induction and challenge in the main study was 50 % and 25 %, respectively.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 1 intradermal, 1 epicutaneous
- Exposure period: intradermal injection on day 1, on day 8 dermal application over 48 hours
Day 1: An area of dorsal skin from the scapular region (approximately 6x8 cm) was clipped free of hair. Three pairs of intradermal injections (0.1 ml/site) were made at the border of a 4 x 6 cm area in the clipped region as follows (Nos 1, 2, 3 in a row on each flank from the cranial to caudal site):
Day 8: One week after the injections, the scapular area (approximately 6x8 cm) was again clipped and shaved free of hair prior to the application.
- Test groups:
Day 1:
1) 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline.
2) The test item, at 10 % in purified water.
3) The test item at 10% in a 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline.
Day 8:
A 2 x 4 cm patch of filter paper was saturated with the test item (50 % in purified water) and placed over the injection sites of the test animals. The amount of test item preparation applied was approximately 0.3 g. The patch was covered with aluminum foil and firmly secured by an elastic plaster wrapped around the trunk of the anima! and secured with impervious adhesive tape. The occlusive dressings were left in place for 48 hours. The epidermal application procedure described ensured intensive contact of the test item.
The reaction sites were assessed 24 and 48 hours after removal of the bandage for erythema and edema accordin to the method of Magnusson and Kligman.
- Control group:
Day 1:
1) 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saiine.
2) Purified water
3) 1:1 (w/w) mixture of purified water in a 1:1 (v/v) mixture of Freund's Complete Adjuvant and physiological saline.
Day 8:
The guinea pigs of the control group were treated as described above with purified water only, applied at a volume of approximately 0.3 ml.
- Site: dorsal skin from the scapular region
- Frequency of applications: single applications
- Duration: single injection resp. 48h dermal application
- Concentrations: 10% (intradermal), 50% (epicutaneous)

B. CHALLENGE EXPOSURE
- No. of exposures: single
The test and control guinea pigs were challenged two weeks after the epidermal induction application and were treated in the same way.
Hair was clipped and shaved from a 5 x 5 cm area on the left and right flank of each guinea pig just prior to the application.
- Day(s) of challenge: day 22
- Exposure period: The dressings were left in place for 24 hours
- Site: flanks
- Concentrations: Two patches (3x3 cm) of filter paper were saturated with the test item at the highest tested non-irritating concentration of 25 % (applied to the left flank) and the vehicle only (purified water applied to the right flank) using the same method as for the epidermal application. The volume of test item preparation or vehicle applied was approximately 0.2 ml.
- Evaluation (hr after challenge): Twenty-one hours after removal of the dressing the test sites treated with the test item were depilated as described in the epidermal pretest.
The reaction sites were assessed 24 and 48 hours after removal of the bandage for erythema and oedema according to the method of Magnusson and Kligman

Challenge controls:

25 % test item in the negative control animals

Positive control substance(s):

yes

Remarks:

ALPHA-HEXYLCINNAMALDEHYDE in a separate study

Positive control results:

The study was performed with 15 (10 test and 5 control) male albino guinea pigs (GOHI).
Switzerland).
The intradermal induction of sensitization in the test group was performed in the nuchal region with a 10 % dilution of the test item in PEG 300 and in an emulsion of Freund's Complete Adjuvant (FCA) / physiological saline. The epidermal induction of sensitization was conducted for 48 hours under occlusion with the test item at 10 % in PEG 300 one week after the intradermal induction. The animals of the control group were intradermaily induced with PEG 300 and FCA/physiological saline and epidermaliy induced with PEG 300 under occlusion. Two weeks after epidermal induction the control and test animals were challenged by epidermal application of the test item at 0.1 % in PEG 300 and PEG 300 alone under occlusive dressing.
Cutaneous reactions were evaluated at 24 and 48 hours after removal of the dressing.

No toxic symptoms were evident in the guinea pigs of the control or test group. No deaths occurred.
All test animals (at the 24 hour reading) and 6 out of 10 animals (at the 48 hour reading) showed discrete/patchy erythema after the challenge treatment with ALPHAHEXYLCINNAMALDEHYDE at 0.1 % (w/w) in PEG 300.
No skin effect was observed in the control group.
Based on the above mentioned findings in an adjuvant sensitization test (M&K test) in guinea pigs and in accordance to Commission Directive 96/54/EEC, ALPHAHEXYLCINNAMALDEHYDE have to be classified and labelled as a skin sensitizer and proved the sensitivity of the test system.

Key result

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

25%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

There were no deaths during the course of the study, hence no necropsies were performed. No signs of systemic toxicity were observed in the animals.

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

25%

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

There were no deaths during the course of the study, hence no necropsies were performed. No signs of systemic toxicity were observed in the animals.

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

25%

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

There were no deaths during the course of the study, hence no necropsies were performed. No signs of systemic toxicity were observed in the animals.

Remarks on result:

no indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

25%

No. with + reactions:

0

Total no. in group:

5

Clinical observations:

There were no deaths during the course of the study, hence no necropsies were performed. No signs of systemic toxicity were observed in the animals.

Remarks on result:

no indication of skin sensitisation

Reading:

1st reading

Hours after challenge:

24

Group:

positive control

Dose level:

ALPHAHEXYLCINNAMALDEHYDE, 0.1 % in PEG 300

No. with + reactions:

10

Total no. in group:

10

Clinical observations:

No toxic symptoms were evident in the guinea pigs of the control or test group. No deaths occurred.

Remarks on result:

positive indication of skin sensitisation

Reading:

2nd reading

Hours after challenge:

48

Group:

positive control

Dose level:

ALPHAHEXYLCINNAMALDEHYDE, 0.1 % in PEG 300

No. with + reactions:

6

Total no. in group:

10

Clinical observations:

No toxic symptoms were evident in the guinea pigs of the control or test group. No deaths occurred.

Remarks on result:

positive indication of skin sensitisation

Interpretation of results:

GHS criteria not met

Conclusions:

The study was conducted according to OECD 406 under GLP without relevant deficiencies, positive and negative controls gave the appropriate response. Hence, the study can be considered as sufficiently reliable to assess the sensitizing potential of the test item in a guinea pig maximisation test.
According to the guideline, a minimum of 10 animals is used in the treatment group and at least 5 animals in the control group. When fewer than 20 test and 10 control guinea pigs have been used, and it is not possible to conclude that the test substance is a sensitizer, testing in additional animals to give a total of at least 20 test and 10 control animals is strongly recommended.
Testing clearly revealed that the substance is not a skin sensitizer, the maximum possible concentrations were used. Although testing of additional animals is strongly recommended, it was considered not scientifically necessary. The GPMT is designed to elicit the maximal possible reaction in case the substance is a sensitizer. None of the animal showed any reactions on any point of time of challenge, so it is considered scientifically reasonable to omit further testing with regard to animal welfare and to safely conclude there is no sensitizing hazard arising from the test item.
According to Regulation 1272/2008, when an adjuvant type guinea pig test method for skin sensitisation is used, a response of at least 30 % of the animals is considered as positive. Hence, no classification as skin sensitizer is required.

Executive summary:

In order to assess the cutaneous allergenic potential of 1,3-Dimethyl-4-aminouracil, the Maximization-Test was performed in 15 (10 test and 5 control) female albino guinea pigs, in accordance with OECD Guideline No. 406 and the Directive 96/54/EEC, B.6, under GLP.

The intradermal induction of sensitization in the test group was performed in the nuchal region with a 10 % dilution of the test item in purified water and in an emulsion of Freund's Complete Adjuvant (FCA) / physiological saline. The epidermal induction of sensitization was conducted for 48 hours under occlusion with the test item at 50 % in purified water one week after the intradermal induction. The animals of the control group were intradermally induced with purified water and FCA/physiological saline and epidermally induced with purified water under occlusion.

Two weeks after epidermal induction the control and test animals were challenged by epidermal application of the test item at 25 % in purified water and purified water alone under occlusive dressing.

Cutaneous reactions were evaluated at 24 and 48 hours after removal of the dressing.

 

Results: Skin reactions after the challenge procedure

	After 24h		After 48h
Animal Numbers	Positive / total	% positive of total	Positive / total	% positive of total
Control Group
1,3-Dimethyl-4-aminouracil at 25 % (w/w) in purified water (left flank)	0/5	0	0/5	0
Purified water only (right flank)	0/5	0	0/5	0
Test group
1,3-Dimethyl-4-aminouracil at 25 % (w/w) in purified water (left flank)	0/10	0	0/10	0
Purified water only (right flank)	0/10	0	0/10	0

 

No toxic symptoms were evident in the guinea pigs of the control or test group.

No deaths occurred

None of the control and test animals showed skin reactions after the challenge treatment with 1,3-Dimethyl-4-aminouracil at 25 % (w/w) in purified water.

Conclusion: Based on the above mentioned findings in an adjuvant sensitization test (M&K-test) in guinea pigs and in accordance to Commission Directive 96/54/EEC and Regulation 1272/2008, 1,3-Dimethyl-4-aminouracil does not have to be classified and labelled as a skin sensitizer.

Reference 2

Endpoint:

skin sensitisation: in vivo (LLNA)

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP, OECD guideline 429 and EU Method B.42

Qualifier:

according to guideline

Guideline:

OECD Guideline 429 (Skin Sensitisation: Local Lymph Node Assay)

Qualifier:

according to guideline

Guideline:

EU Method B.42 (Skin Sensitisation: Local Lymph Node Assay)

GLP compliance:

yes

Type of study:

mouse local lymph node assay (LLNA)

Species:

mouse

Strain:

other: CBA/CaOlaHsd

Sex:

female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Harlan Laboratories B.V. , Postbus 6174, 5960 AD Horst / The Netherlands
- Age at study initiation: 8 - 12 weeks
- Weight at study initiation: 19 - 22 g
- Housing: single; Cage Type: Makrolon Type II, with wire mesh top (EHRET GmbH, 79302 Emmendingen, Germany); Bedding: Granulated soft wood be dding (Rettenmaier & Söhne GmbH + Co. KG, 73494 Rosenberg, Germany)
- Diet (e.g. ad libitum): pelleted standard diet; Harlan Laboratories B.V., 5960 AD Horst / Netherlands
- Water (e.g. ad libitum): tap water, Gemeindewerke, 64380 Rossdorf, Germany
- Acclimation period:

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 - 24
- Humidity (%): 18 - 65
- Photoperiod (hrs dark / hrs light): 12 / 12

Vehicle:

dimethyl sulphoxide

Concentration:

5, 10, and 20% (w/w) in dimethylsulfoxide

No. of animals per dose:

4

Details on study design:

for details on study design see "Any other inrofmation on materials and methods incl. tables".

Positive control substance(s):

hexyl cinnamic aldehyde (CAS No 101-86-0)

Statistics:

The mean values and standard deviations were calculated in the body weight tables. The ANOVA (Dunnett-test) was conducted on the ear and lymph node weights to assess whether the difference is statistically significant between test item groups and negative control (vehicle) group. However, both biological and statistical significance were considered together.

Positive control results:

Positive control substance: alpha-Hexylcinnamaldehyde
Test item concentration % (w/v) S.I.
0 1.00
5 1.21
10 2.09
25 6.22

Parameter:

SI

Remarks on result:

other: see Remark

Remarks:

Test item concentration % (w/v) SI 0 - 5 1.31 10 1.46 20 2.25 None of the tested concentrations induced an S.I. greater than 3.

Parameter:

other: disintegrations per minute (DPM)

Remarks on result:

other: see Remark

Remarks:

Test item concentration % (w/v) Measurement DPM 0 3172 5 4150 10 4623 20 7122

Test item concentration % (w/w)	Group	Measurement DPM	Calculation			Result
			DPM-BG^a)	number of lymph nodes	DPM per lymph node^b^)	S.I.
---	BG I	15	---	---	---	---
---	BG II	20	---	---	---	---
0	1	3172	3155	8	394.3
5	2	4150	4133	8	516.6	1.31
10	3	4623	4606	8	575.7	1.46
20	4	7122	7105	8	888.1	2.25

Vehicle: DMSO

BG  =  Background (1 ml 5% trichloroacetic acid) in duplicate

1     =  Control Group

2-4 =  Test Group

S.I. =  Stimulation Index

^a)    =  The mean value was taken from the figures BG I and BG II

^b)    =  Since the lymph nodes of the animals of a dose group were pooled, DPM/node was determined by dividing the measured value by the number of lymph nodes pooled

The EC3 value could not be calculated, since all S.I.´s are below 3.

Interpretation of results:

not sensitising

Remarks:

Migrated information

Conclusions:

The test item 1,3-Dimethyl-4-aminouracil was not a skin sensitiser under the test conditions of this study.

Executive summary:

At the tested concentrations the animals did not show any signs of systemic toxicity. Also, the animals did not show relevant signs of local irritation as confirmed by the ear thickness and ear weight measurements. Applied to the skin of mice, the test item was not a sensitiser.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

In the available key study (GPMT), none of the animals showed any reaction after challenge. According to Regulation 1272/2008, when an adjuvant type guinea pig test method for skin sensitisation is used, a response of at least 30 % of the animals is considered as positive. Hence, no classification as skin sensitizer is required.This is supported by the available LLNA, in which the SI was not exceeding 3 at the maximal possible concentration.