Registration Dossier

Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
No data
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP, guideline study
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2005

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 428 (Skin Absorption: In Vitro Method)
Deviations:
no
Remarks:
Not specified in report
Qualifier:
according to
Guideline:
other: OECD Draft Guidance Document for the Conduct of Skin Absorption Studies. OECD Environmental Health and Safety Publications Series on Testing and Assessment No. 28. (2002)
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Source (non-radiolabel): Angus Chemical Company
Sopurce (radiolabel): Moravek Biochemicals, Inc. (Brea, California)
Non-radiolabel material had a purity of 99.5%.
Radiolabeled: radiochemical purity 99.1%, Sp. Act. 32 mCi/mmol
Radiolabelling:
yes
Remarks:
[14C]1-nitropropane, was supplied by the sponsor and obtained from Moravek Biochemicals, Inc. (Brea, California) and assigned Haskell Laboratory Number 22705-101. The test substance had a radiochemical purity of 99.1% and a specific activity of 32 mCi/mm

Test animals

Species:
human
Strain:
other: Not applicable
Sex:
male/female
Details on test animals and environmental conditions:
Samples of human cadaver skin from the National Disease Research Interchange (NDRI) were stored frozen at approximately -20°C until prepared for use. Samples were removed from donors within 24 hours of death and used within three months. Skin specimens selected for use were identified using a unique code (e.g., HCFA-26A = Human, Caucasian, Female, Abdomen sample 26-A).

Administration / exposure

Type of coverage:
other: Permeability coefficient experiment-donor chamber opening was occluded with a rubber stopper; for the short-term exposure experiments, the donor chamber opening was covered with a volatile organic trap.
Vehicle:
unchanged (no vehicle)
Duration of exposure:
Permeability coefficient experiment- 8 hours
Short-term exposure experiments- 10 and 60 minutes
Doses:
Permeability coefficient experiment- 1200 μL/cm2
Short-term exposure experiments- 20 μL/cm2
No. of animals per group:
Permeability coefficient experiment- 6 skin replicates representing 3 human subjects
Short-term exposure experiments- 6 skin replicates/exposure time representing 3 human subjects
Control animals:
no
Details on study design:
The permeability coefficient (Kp) and the short-term absorption rates at 10 and 60 minutes have been determined for 1-nitropropane using human abdominal skin from cadavers mounted in an in vitro static diffusion cell model. Human cadaver skin was heat-treated at approximately 60°C and the epidermis was peeled from the dermis and the section mounted onto an in vitro static diffusion cell, stratum corneum uppermost, with an exposure area of 0.64 cm2. Using a recirculating water bath system, the receptor fluid (0.9% saline) was maintained at 32°C. Following system equilibration, skin integrity was confirmed by electrical impedance (EI). The saline in the donor and receptor chambers was removed and discarded and the receptor chamber was filled with 0.9% saline fortified with 6% polyethoxyoleate (polyethylene glycol (PEG) 20 oleyl ether).

For the permeability coefficient experiment, an infinite dose of 1-nitropropane was applied to the epidermal surface, via the donor chamber, at a target rate of 1200 μL/cm2, to 6 skin replicates representing 3 human subjects, and the donor chamber opening was occluded with a rubber stopper. Serial receptor fluid samples were taken at 0.5, 1, 2, 3, 4, 5, 6, and 8 hours postapplication and analyzed for radioactivity by liquid scintillation counting. At the end of the 8- hour exposure, excess 1-nitropropane was removed and the skin washed with a 2% soap solution followed by rinsing with water. The receptor fluid was removed and discarded. The receptor and donor chambers were filled with 0.9% saline and an end of experiment integrity asssessment was determined using EI.

For the short-term exposure experiments, a finite dose of 1-nitropropane (20 μL/cm2) was applied to the epidermal surface, via the donor chamber, to 12 skin replicates representing 3 human subjects, and the donor chamber opening was covered with a volatile organic trap. At the end of the required exposure interval (10 minute and 60 minutes), 6 replicates each were terminated. At termination, the volatile trap was removed and extracted with ethanol. The skin surface was washed with a 2% soap solution, rinsed with water, and the receptor fluid was removed and retained for analysis. The receptor and donor chambers were filled with 0.9% saline and end of experiment integrity asssessment was taken using EI. The saline in both chambers was removed and the donor chamber was retained for analysis. The skin membrane was removed and placed into a glass vial for digestion. The receptor fluid and the skin were analyzed by liquid scintillation counting.
Details on in vitro test system (if applicable):
See study design above

Results and discussion

Signs and symptoms of toxicity:
not examined
Dermal irritation:
not examined
Absorption in different matrices:
See "remarks on results" below
Total recovery:
Permeability Coefficient: Recovery of the applied radioactive dose was 83.3%.

10- and 60- Minute Short Term Penetration Rates: Recovery of the applied radioactive dose was 76.9 and 78.5% for the 10- and 60-minute exposure groups, respectively.
Percutaneous absorption
Remarks on result:
other: See "remarks on results" below
Conversion factor human vs. animal skin:
Not applicable

Any other information on results incl. tables

Based on the slope at steady-state (179.6 μg equiv/cm2/h) and the concentration of the applied dose of 1-nitropropane taken as its density (998,000 μg/cm3), the permeability coefficient was calculated to be 1.80 x 10-4 cm/h.

Following a 10-minute exposure to a finite application of 1-nitropropane, a total of 127.2 μg equivalents of 1-nitropropane were detected in the receptor fluid, with 5.40 μg equivalents in the skin. Based on the amount of 1-nitropropane in the receptor fluid and skin, an exposure area of 0.64 cm2, and an exposure time of 10 minutes (0.17 hours), the short-term penetration rate was calculated to be 1218.5 μg equiv/cm2/h.

Following a 60-minute exposure to a finite application of 1-nitropropane, a total of 108.5 μg equivalents of 1-nitropropane were detected in the receptor fluid and 6.00 μg equivalents in the skin. Based on the amount of 1-nitropropane in the receptor fluid and skin, an exposure area of 0.64 cm2, and an exposure time of one hour, the short-term penetration rate was calculated to be 178.9 μg equiv/cm2/h.

Applicant's summary and conclusion

Conclusions:
Based on the slope at steady-state (179.6 μg equiv/cm2/h) and the concentration of the applied dose of 1-nitropropane taken as its density (998,000 μg/cm3), the permeability coefficient was calculated to be 1.80 x 10-4 cm/h.

Following a 10-minute exposure to a finite application of 1-nitropropane, a total of 127.2 μg equivalents of 1-nitropropane were detected in the receptor fluid, with 5.40 μg equivalents in the skin. Based on the amount of 1-nitropropane in the receptor fluid and skin, an exposure area of 0.64 cm2, and an exposure time of 10 minutes (0.17 hours), the short-term penetration rate was calculated to be 1218.5 μg equiv/cm2/h.

Following a 60-minute exposure to a finite application of 1-nitropropane, a total of 108.5 μg equivalents of 1-nitropropane were detected in the receptor fluid and 6.00 μg equivalents in the skin. Based on the amount of 1-nitropropane in the receptor fluid and skin, an exposure area of 0.64 cm2, and an exposure time of one hour, the short-term penetration rate was calculated to be 178.9 μg equiv/cm2/h.
Executive summary:

None