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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:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference
Reference Type:
publication
Title:
Percutaneous absorption of thirty-eight organic solvents in vitro using pig skin
Author:
Schenk L, Rauma M, Fransson MN, Johanson G
Year:
2018
Bibliographic source:
PLoS ONE 13(10): e0205458. https://doi.org/ 10.1371/journal.pone.0205458

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
A larger number of organic solvents was tested with the same experimental set up, using skin from new-born piglets and static diffusion cells. Thirty-six common organic solvents were studied neat (and 31 of them also in water dilution). Lag times, steady-state fluxes and apparent permeability coefficients were obtained from the time courses of solvent appearance in the receptor medium, as measured by gas chromatography.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Specific details on test material used for the study:
3-methyl-1-butanol (123-51-3, 2:99.0%) was obtained from Merck (Darmstadt, Germany).
Radiolabelling:
no

Test animals

Species:
pig
Strain:
other: Duroc
Sex:
not specified
Details on test animals and environmental conditions:
Piglets (Duroc) that had died of natural causes (at birth or first week of life) were obtained from local commercial breeders. As this source of skin is categorised as slaughter waste, it is exempt from the Swedish Board of Agriculture' s requirements on ethical vetting of research involving animals.
Pig skin has been shown to be similar to human skin with respect to stratum corneum and epidermal thickness as well as permeability. Skin specifically from new-born pigs that died of natural causes has also been shown to be a suitable replacement for human skin by Cilurzo et al., as their experimentally derived in vitro fluxes for seven benzoxaznones were within a factor of 2 from previously published data on human epidermis.

Administration / exposure

Details on study design:
For early experiments dermatomed skin (n = 10) was employed and then proceeded to use full-thickness skin. In both cases, skin pieces measuring approximately 8 x 5 cm2 were collected from the back and flank of the piglet. Each skin piece was stretched around the edges of a soft polyethene plate (21 x 3 x 0.7 cm3) and fastened to the sides of the plate with a staple gun. Another plate, wrapped in polyethene film, served as a lid and was
placed on top of the skin and firmly and evenly fixed to the bottom plate by bolts and nuts. The mounted skin pieces were stored at-20"C. In those cases skin was dermatomed, it was taken out after 12 h and the frozen piece dermatomed (Model C, Padgett Instruments, Inc., Kansas City, MO). Dermatomed skin pieces were wrapped in aluminium foil and polyethene film, and then stored at -20"C until later use. Twenty four hours before study the skin pieces were thawed for 15 minutes in room temperature. Thereafter the thickness was measured by using a micrometer (293-661-10, Mitutoyo) and integritywas checked by an ohm meter (Fluke 111, Fluke Corporation, Everett, WA, USA). Pieces with a resistance below 50 kn were discarded. This cut-off was validated against in house measurements of intact and damaged skin pieces. The skin pieces were stored overnight
in saline at +8'C prior to permeation measurements.
Six jacketed static Franz cells (orifice diameter 9 mm, corresponding to a skin exposure area of 0.64 cm2, receptor volume 5.0-5.4 mL, model number 4G-0 1-00-090-05, Permegear, Bethlehem, PA, USA) were mounted in a magnetic stirrer (HP 6 Variomag, H + P Labortechnik, Munich, Germany) and kept at 32'C by means of circulating water from a thermostatted water bath (21 AT, Heto, Allre0d, Denmark). Degassed phosphate buffered saline (1000-3, Sigma-Aldrich, Steinheim, Germany) containing 6% PEG-20 oleyl ether (P5641, Sigma-Aldrich, Steinheim, Germany), according to OECD guidelines, was used as receptor fluid. The receptor compartment was kept well stirred using Teflon coated magnets. Skin pieces were mounted onto the Franz cells one hour before start of exposure. At start of experiment, the donor compartment was filled with excess test chemical (approximately 1 ml, neat or diluted in water) and capped with a glass stopper. Experiments ran for 4 to 9 hours. Aliquots of receptor fluid (50 μl) were sampled at predefined times (every 10 min first hour, every 20 min second hour, then every 30 min) using a gas-tight syringe (004250, SGE, Victoria, Australia). Samples were directly transferred to head-space glass vials, which were immediately capped and stored at +8'C for later analysis (within two days) by head-space gas chromatography.

Results and discussion

Percutaneous absorptionopen allclose all
Dose:
100%
Parameter:
other: Permeability coefficient
Absorption:
0 cm/h
Dose:
1%
Parameter:
other: Permeability coefficient
Absorption:
0.012 cm/h

Any other information on results incl. tables

The tested solvent showed skin permeabilities (Kp) ranging from "moderate" (10-4 cm/h) to "very high" (10-2 cm/h) according to previously proposed classification schemes depending on the concentration applied.

Applicant's summary and conclusion