Registration Dossier

Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
31 Jan - 3 Feb 2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to test guidelines and in accordance with GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2000
Report Date:
2000

Materials and methods

Test guidelineopen allclose all
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 428 (Skin Absorption: In Vitro Method)
Qualifier:
according to
Guideline:
other: The recommendations of the OSHA (TSCA, Section 4, ITC) published in the Federal Register (1999), which references a protocol Bronaugh R L and Collier S W (1991). Protocol for In vitro Percutaneous Absorption studies. In Vitro Percutaneous Absorption : Pr
Principles of method if other than guideline:
Study was conducted prior to acceptance of actual guidelines but followed intent of the guidelines
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
Test material purity was 99.8%
Radiolabelling:
no

Test animals

Species:
human
Strain:
not specified
Sex:
not specified
Details on test animals and environmental conditions:
Extraneous tissue was removed from human whole skin samples obtained post mortem. The skin samples were immersed in water at 60°C for 40-45 seconds and the epidermis teased away from the dermis. Each epidermal membrane was given an identifying number and stored frozen on aluminium foil until required for use.

Administration / exposure

Type of coverage:
open
Vehicle:
unchanged (no vehicle)
Duration of exposure:
24 hr
Doses:
100ul/cm2
No. of animals per group:
5
Control animals:
no
Details on study design:
See other sections
Details on in vitro test system (if applicable):
Measurement of membrane integrity
Samples of epidermis were mounted in glass diffusion cells with an exposed area of 2.54cm2. The cells were placed in a water bath maintained at 32 +/- 1°C.

The integrity of the membranes was determined by measurement of their electrical resistance across the skin membrane. Membranes with a measured resistance <10kOhm were regarded as having a lower integrity than normal.

Measurement of test substance absorption
The receptor chambers of the cells were filled with a recorded volume of receptor fluid (50% ethanol in water) and placed in a water bath maintained at 32 & 1°C. This receptor fluid adequately solubilises the test chemical. A pre-treatment sample was taken from each receptor chamber for analysis by gas-liquid chromatography GLC. An equal volume of fresh receptor fluid was added to each receptor chamber to replace the volume removed.

The primary amyl acetate isomer mixture was applied undiluted to the skin membranes at a dose rate of 100yl/cm2 and left unoccluded for the duration of the exposure period (24h).

At recorded intervals (pre-treatment, 0.17,0.5, 1,2, 3,4,6, 8, 10, 12, 16, 20 and 24h) 0.5ml samples of the receptor fluid were taken for analysis by GLC. The volume of fluid in the receptor chamber was maintained by the addition of 0.5ml fresh receptor fluid to the chamber immediately after the removal of each sample.

Iso-hexane (0.5ml) was added to the receptor fluid samples and the whole shaken vigorously for 30 seconds. Where emulsions between the two phases occurred, 50yl of a 10% sodium chloride solution was added. After the two phases separated, the lower aqueous phase carefully drawn off using a syringe and discarded. The remaining iso-hexane extract was left in the vial and analysed for the amyl acetate isomers.

Results and discussion

Signs and symptoms of toxicity:
not specified
Dermal irritation:
not specified
Absorption in different matrices:
The absorption profiles for both isomers of amyl acetate were similar and the absorption rates were essentially constant after the first 6h of exposure. The 2-methylbutyl acetate isomer was absorbed at a rate of 47.8ug/cm2/h (Kp = 1.56 x 10(-4) cm/h), while the pentyl acetate isomer
was absorbed at a somewhat faster rate of 123ug/cm2/h (Kp = 2.16 x 10(-4)cm/h).
Conversion factor human vs. animal skin:
study conducted with human skin

Any other information on results incl. tables

No additional information available.

Applicant's summary and conclusion

Conclusions:
The absorption rates for both isomers of amyl acetate were essentially constant after the first 6h of exposure. The 2-methylbutyl acetate isomer was absorbed at a rate of 47.8μg/cm2/h (Kp = 1.56 x 10(-4) cm/h), while the pentyl acetate isomer was absorbed at a rate of 123μg/cm2/h (Kp = 2.16 x 10(-4) cm/h).
Executive summary:

The absorption of primary amyl acetate isomers from a 35:65 mix of 2-methylbutyl acetate and pentyl acetate has been measured in vitro through human epidermis. The primary amyl acetate mixture was applied undiluted at a rate of 100μl/cm2 and left occluded throughout the entire exposure period (24h).

The absorption rates for both isomers of amyl acetate were essentially constant after the first 6h of exposure. The 2-methylbutyl acetate isomer was absorbed at a rate of 47.8μg/cm2/h (Kp = 1.56 x 10-4 cm/h), while the pentyl acetate isomer was absorbed at a rate of 123μg/cm2/h (Kp = 2.16 x 10-4 cm/h).

The results obtained in this study indicate that the 2-methylbutyl acetate and pentyl acetate isomers are moderately well absorbed through human epidermis when compared with the absorption rates of other penetrants measured using this in vitro technique (Dugard et al, 1984; Dugard and Scott, 1984).

The pentyl acetate isomer is absorbed through human epidermis at a faster rate than 2- methylbutyl acetate isomer.