Registration Dossier

Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Not applicable
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP-study equivalent to OECD guideline.
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:
1986
Report Date:
1986

Materials and methods

Principles of method if other than guideline:
This study was designed to determine the absorption rate of EEP through rat skin in vitro and to assess the damage caused by the contact of the chemical with the skin. For a large number of compounds, good agreement has been found between the results of vivo and in vitro skin permeability studies. The procedure followed in this study employed Franz-type glass diffusion cells, in which the skin sample formed a membrane between two chambers, one of which contained an excess of EEP, and another which acted as a receptor for the chemical after skin penetration.
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Ethyl 3-ethoxypropionate (EEP, E.K. Acc. #906315, HAEL #83-0169, CAS #763-69-9) was obtained from Tennessee Eastman Company, Kingsport, TN (SRID # X-18626-184-7). Radioactively labeled EEP ([propionyl-2-14C] EEP) was purchased from New England Nuclear Corporation (Boston, MA) with a specific radioactivity of 0.725 mCi per mmole (about 5.0 µCi per mg). Prior to use, both labeled and unlabeled EEP were analyzed for purity by gas chromatography. Structural confirmatifon of the unlabeled EEP was obtained by mass spectrometry.
Radiolabelling:
yes

Test animals

Species:
rat
Strain:
Sprague-Dawley
Sex:
male
Details on test animals and environmental conditions:
Animals
Full thickness skin samples were obtained from male Sprague-Dawley [COBS-CD-(SD)Br] rats weighing 264-284 g, obtained from Charles River Laboratories, Wilmington, MA. Each rat was identified with a uniquely numbered ear tag. Water and food (Agway Prolab Animal Diet RMH 3000 Certified pellets) was available ad libitum until time of sacrifice.

Administration / exposure

Duration of exposure:
Not applicable
Doses:
Tritiated Water: specific radioactivity - 0.00293 µCi/mg: Concentration 1000 mg/mL;
specific radioactivity - 0.00331 µCi/mg: Concentration 1000 mg/mL;
14C-EEP: specific radioactivity - 0.00201 µCi/mg: Concentration 954.200 mg/mL
No. of animals per group:
Not applicable
Details on study design:
Not applicable
Details on in vitro test system (if applicable):
SKIN PREPARATION
- Source of skin: Full thickness skin samplesw ere obtained from male Sprague-Dawley [COBS-CD-(SD)Br] rats weighing 264-284 g, obtained from Charles River Laboratories, Burlington, MA.
- Type of skin: abdominal skin
- Preparative technique: Skin samples were taken immediately prior to starting the first day of the study. For each experiment, 4 skin samples were taken from each of 2 animals. On the first day, the test animals were euthanized using CO2 and the abdominal surface shaved carefully. The abdominal skin was removed from the animals and trimmed of excess fat and muscle tissue.
- Thickness of skin (in mm):
- Membrane integrity check: The integrity of each skin sample was determined by measuring its permeability to tritiated water ( 3H2O, approximately
1 µCi per skin sample)
- Storage conditions:
- Justification of species, anatomical site and preparative technique:


PRINCIPLES OF ASSAY
- Diffusion cell: Franz-type cell
- Receptor fluid: isotonic saline containing an antibiotic-antimycotic solution (Penicillin, Fungizone®and Streptomycin, GIBCO Laboratories, Grand Island, NY).
- Solubility of test substance in receptor fluid:
- Static system:
- Flow-through system:
- Test temperature: 37ºC
- Humidity:
- Occlusion:
- Reference substance(s):
- Other:

Results and discussion

Absorption in different matrices:
Not applicable
Percutaneous absorption
Dose:
954.2 mg/mL
Parameter:
percentage
Absorption:
2.2 %
Remarks on result:
other: Mean measurement
Remarks:
S.E.M. = 0.07. The absorption rate was calculated from the rate of increase of 14C or 3H concentration in the receptor chamber. Units= mg.cm-2.hr-1
Conversion factor human vs. animal skin:
These experiments allow the estimation of EEP uptake after skin exposure in humans, assuming that the rate of skin absorption for man is similar to that determined for rat. The body surface area of a 70 kg man 180 cm (71 inches) in height is about 1.85 m2, of which about 4% is the surface area of the hands. If the hands were immersed in EEP for 1 hour, the total amount of the chemical absorbed would be 1650 mg, or about 23.6 mg/kg. This value probably overestimates the potential absorption of EEP in man, since, for a number of chemicals, human skin is markedly less permeable than rodent skin.

Any other information on results incl. tables

No significant difference was found between the permeability constants for14C-EEP on day 2, based on the experiment number or rat number. The pooled mean permeability constant for14C- EEP was 2.33 x 10-3cm.hr-1( ±0-07, SEM). This was equivalent to a mean absorption rate of 2.23 mg.cm-2hr-1.

No significant difference was found between the permeability constants for3H2O on day 1 based on the experiment number or rat number. The pooled mean permeability constant for3H2O prior t o exposure to EEP was 3.11 x 10-3cm .hr-1( ± 0.13, SEM). No significant difference was found in the permeability of the test cell samples to3H2O on day 3 based on the experiment number or rat number. The pooled mean permeability constant for3H20 on day 3 after exposure to EEP was 16.40 x 10-3cm.hr-1( ±1.92, SEM). The pooled mean permeability constant for3H2O on day 3 for control cells (not exposed to EEP) was 4.28 x 10-3cm.hr-1( ± 0 .34, SEM). Thus exposure to the chemical caused a small but significant increase in the permeability of rat skin, as demonstrated by a mean damage ratio of about 5.3, compared with a damage ratio of about 1.4 for skin not exposed to EEP.

Applicant's summary and conclusion

Conclusions:
Exposure to the chemical caused a small but significant increase in the permeability of rat skin, as demonstrated by a mean damage ratio of about 5.3, compared with a damage ratio of about 1.4 for skin not exposed to EEP.
Executive summary:

This study was designed to determine the absorption rate of EEP through rat skin in vitro using Franz-type glass diffusion cells. For each experiment, four full thickness skin samples were taken from each of 2 male Sprague-Dawley [COBS-CD-(SD)Br] rats immediately prior to starting the first day of the study. The integrity of each skin sample was determined by measuring its permeability to tritiated water (3H2O). The study consisted of duplicate 3-day experiments, in which the permeability to3H2O was determined on days 1 and 3, and the permeability to [propionyl-2-14C] EEP (14C-EEP) was determined on day 2. The rate of increase in the concentration of radioactivity in the receptor chamber of each cell was used to calculate a permeability constant (cm.hr-1) and an absorption rate (mg.cm-2.hr-1) for EEP or3H2O. The mean permeability constant for14C-EEP was 2.33 x 10-3cm.hr-' ( ±0.07, SEM). This was equivalent to a mean absorption rate of 2.23 mg.cm-2.hr-1. The mean permeability constant for3H2O prior to exposure to EEP was 3.11 x l0-3cm.hr-1(±0.13, SEM). The mean per The mean permeability constant for14C-EEP was 2.33 x 10-3cm.hr-' ( ±0.07, SEM). This was equivalent to a mean absorption rate of 2.23 mg.cm-2.hr-1. The mean permeability constant for3H2O prior to exposure to EEP was 3.11 x l0-3cm.hr-1(±0.13, SEM). The mean permeability constant for3H2O on day 3 after exposure to EEP was 16.40 x 10-3cm.hr-1(±1.92, SEM). The mean permeability constant for3H2O day 3 for control cells (not exposed to EEP) was 4.28 x 10-3cm.hr" ( ± 0.34, SEM). Thus exposure to the chemical caused a small but significant increase in the permeability of rat skin, as demonstrated by a mean damage ratio of about 5.3, compared with a damage ratio of about 1.4 for skin not exposed to EEP. These experiments allow the estimation of EEP uptake after skin exposure in humans, assuming that the rate of skin absorption for man is similar to that determined for rat. The body surface area of a 70 kg man 180 cm (71 inches) in height is about 1.85 m2, of which about 4% is the surface area of the hands. If the hands were immersed in EEP for 1 hour, the total amount of the chemical absorbed would be 1650 mg, or about 23.6 mg/kg. This value probably overestimates the potential absorption of EEP in man, since, for a number of chemicals, human skin is markedly less permeable than rodent skin.