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Toxicological information

Dermal absorption

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Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Cross-reference
Reason / purpose:
reference to same study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1993

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 428 (Skin Absorption: In Vitro Method)
Principles of method if other than guideline:
Investigation of percutaneous absorption of 4.4'-methylenedianiline (MDA) after topical application to full-thickness skin from male Fischer 344 rats in flow-through diffusion cells, on four separate occasions.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Specific details on test material used for the study:
RADIOLABELLING INFORMATION
- Radiochemical purity: >95%
- Specific activity: 56 mCi/mmol
- Locations of the label: [ring14C]4,4 '-methylenedianiline (Amersham)
Radiolabelling:
yes

Test animals

Species:
rat
Strain:
Fischer 344
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Harlan-OLAC (Oxford, Oxon, UK)
- Diet: CRM pellets, Biosure (Manea, Cambs., UK); ad libitum
- Water: ad libitum

Administration / exposure

Type of coverage:
other: occlusive and open
Vehicle:
ethanol
Duration of exposure:
72 h
Doses:
- Actual doses: 39.4, 20.1, 21.6, 23.6 µg/cm²
- Dose volume: 5-10 µL
No. of animals per group:
4
Details on in vitro test system (if applicable):
SKIN PREPARATION
- Source of skin: dorsal region of male Fischer 344 rats
- Type of skin: full thickness
- Preparative technique: following sacrificion, the dorsal region was shaved with animal clippers and the shaved area was cut out with dissecting scissors. The rat skin sections were placed, epidermal side uppermost, on a plastic dissecting board and circles, 1.7 cm in diameter, were cut out using a circular sharpened steel cutter. Excess subcutaneous tissue was removed with a scalpel.

PRINCIPLES OF ASSAY
- Flow-through diffusion cell system: consisted of seven teflon diffusion cells and a fraction collector (Crown Glass Co Inc., Somerville, NJ, USA), a thermostatically controlled Churchill water circulator and a model 202V/AA16 cassette peristaltic pump (Watson-Marlow, Falmouth, Cornwall, UK). The receptor volume of each diffusion cell was 130 ul.
- Receptor fluid: HEPES buffered Hanks' balanced salt solution supplemented with 0.5% (v/v) gentamicin, continuously flowing
- Test temperature: 32°C
- the skin was placed in the diffusion cells in the flow-through apparatus, and allowed to equilibrate for about 30min.
- aliquots of 5-10 µL [14C]-MDA (17.7-40.6 µg/cm²) in ethanol were applied to the exposed skin surface.
- occlusion with teflon caps or left open.
- receptor fluid (1.5 mL) was collected hourly for up to 72h.
- at the end of the experiment (72h) the epidermal surface of the skin was washed, and the washings and skin were counted to determine radioactivity remaining on the skin surface.

ANALYSIS
- Liquid scintillation counting

STATISTICAL EVALUATION:
- Student`s t-Test for unpaired data, level of significance p<0.05.

Results and discussion

Absorption in different matrices:
See table 1
Total recovery:
- Total recovery: 94.5 +/-6 %
Percutaneous absorptionopen allclose all
Dose:
20.1-39.4 µg/cm³
Parameter:
percentage
Absorption:
ca. 6.1 %
Remarks on result:
other: 72 h
Remarks:
open
Dose:
20.1-39.4 µg/cm²
Parameter:
percentage
Absorption:
ca. 13.3 %
Remarks on result:
other: 72h
Remarks:
occlusive

Any other information on results incl. tables

Table 1: Recovery of radioactivity at 72h after topical application of [14C] MDA to rat skin in vitro (% of applied dose).

Rat (unoccluded) (n=12) Rat (occluded) (n=16)
Receptor fluid 6.1 ± 2 13.3 ± 4.0*
Skin surface 25.5 ± 6.8 21.5 ± 7.2
Diffusion cell 5.4 ± 4.4 3.9 ± 2.6
Teflon cap - 0.3 ± 0.2
Skin surface 57 ± 5.6 53.1 ± 8.6
Total 94.5 ± 6.0 92.1 ± 6.5

* significantly different from unoccluded value (p<0.05)

A typical absorption profile showed a lag phase of about 2 hr before a rapid increase in absorption, reaching an equilibrium at 72 hr (data not shown).

Applicant's summary and conclusion