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Dermal absorption

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Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well documented, meets generally accepted scientific principles, acceptable for assessment
Cross-reference
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
publication
Title:
In vitro percutaneous absorption of nonylphenol (NP) and nonylphenol ethoxylates (NPE-4 and NPE-9) in isolated perfused skin
Author:
Monteiro-Riviere NA et al.
Year:
2003
Bibliographic source:
J. Cut. Ocul. Tox. 22(1):1-11

Materials and methods

Principles of method if other than guideline:
The isolated perfused porcine skin flap (IPPSF), created on the porcine ventral abdomen, was used in this study. Two single-pedicle axial pattern skin flaps, each lateral to the ventral midline on the pig abdomen, were created during stage 1 and harvested during stage 2 surgery. The flaps were cannulated, flushed to clear the vasculature of blood, and transferred to a perfusion chamber. The flaps were perfused for 1 h prior to dosing, during which arterial and venous samples were collected to determine glucose utilization and zero-time perfusate samples for flux determinations. A stomahesive template was secured to the flap with skin-bond. The skin flap was returned to the chamber and dosed with radiolabeled test substance and after the perfusion was resumed. Perfusate samples were later collected and analyzed for glucose and radioactivity.The remaining venous efflux was collected for 14C determination. The flap and cradle were removed from the flap chamber and rinsed for recovery and the dose area was washed. The tape strips were placed in vials containing ethyl acetate for estimation of stratum corneum penetration.

Flow-through diffusion cell system (PSFT): Pig skin was dermatomed and circular sections were mounted epidermal side up in diffusion cell blocks. Skin was equilibrated in the diffusion cell chambers prior to dosing. A constant perfusate flow rate was maintained during the study. Treatments were dosed with test substance to a nonoccluded areal and perfusate was collected during the study. At the completion of the study tape strips were collected for estimation of stratum corneum penetration. The upper half of the chamber was rinsed and the wash collected for mass balance determination. The remaining skin section was divided into dosing site and peripheral tissue. Perfusate and all tissue samples were then analyzed for total 14C determination
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Nonylphenol (NP)
- Substance type: Nonionic surfactant
- Other: Specific activity 2.214 mCi/mmol
Radiolabelling:
yes

Test animals

Species:
pig
Strain:
other: PSFT study: Yorkshire pig
Sex:
not specified

Administration / exposure

Type of coverage:
other: IPPSF study: occlusive; PSFT study: nonocclusive
Vehicle:
other: PEG-400
Duration of exposure:
IPPSF: 8 h
PSFT: 10 h
Doses:
1%
No. of animals per group:
4 replicates
Control animals:
no
Details on study design:
DOSE PREPARATION
- Method for preparation of dose suspensions:
IPPSF: 100 µL of 1% radiolabeled test substance was mixed with 79% aqueous PEG-400
PSFT: 10 µL of 1% radiolabeled test substance was mixed with PEG-400

APPLICATION OF DOSE: 1%

VEHICLE
- Justification for use and choice of vehicle (if other than water): The 1% aqueous PEG-400 solutions were selected for use in these studies since the previous work had indicated that absorption was not altered by vehicle (PEG-400 vs. water) or by concentration (0.1, 1.0, or 10%)
- Concentration (if solution):
IPPSF: 79%
PSFT: Not reported

TEST SITE
- Preparation of test site:
IPPSF:The flaps were cannulated, flushed with heparinized saline to clear the vasculature of blood, and each transferred to a perfusion chamber. The flaps were perfused for 1 h prior to dosing, during which 1.0-ml arterial and 3.0-ml venous samples were collected at 30 and 60 min to determine glucose utilization and zero-time perfusate samples for nonylphenol flux determinations. Upon confirming flap viability, the perfusion was interrupted and each flap was removed from the chamber.

PSFT: Pig skin was dermatomed using a padgett dermatome (Kansas City, MO). Circular sections were mounted epidermal side up in the teflon diffusion cell blocks. Skin was equilibrated in the diffusion cell chambers for 30 min prior to dosing.
- Area of exposure:
IPPSF: 5.0 cm2
PSFT: 0.32 cm2
- Type of cover / wrap if used:
IPPSF: A stomahesive (ConvaTec, Princeton NJ) template secured with skin-bond (Smith & Nephew, Inc., Largo, FL).

SITE PROTECTION / USE OF RESTRAINERS FOR PREVENTING INGESTION: Not applicable

REMOVAL OF TEST SUBSTANCE
- Removal of protecting device:
IPPSF: The flap and cradle were removed from the flap chamber and rinsed for recovery.
- Washing procedures and type of cleansing agent:
IPPSF: The dose area was swabbed with a mild soap solution to remove nonpenetrated chemical and tape stripped 12 times
PSFT: The application site was swabbed with soapy solution
- Time after start of exposure: After completion of the studies

SAMPLE COLLECTION
- Collection of blood:
IPPSF: While the flaps were perfused for 1 h prior to dosing, 1.0 ml arterial and 3.0 ml venous samples were collected at 30 and 60 min
- Preparation of samples:
IPPSF: Perfusate samples that were collected during the study were analyzed for glucose and radioactivity. Remaining venous efflux was thoroughly stirred and a 3.0 ml sample collected for 14C determination. The tape strips were placed in vials containing ethyl acetate for estimation of stratum corneum penetration. The remaining tissue from the dose site and the entire flap were completely digested in soluene-350.
PSFT: The cellophane tape strips were collected for estimation of stratum corneum penetration.The upper half of the chamber was rinsed and the wash collected for mass balance determination. The remaining skin section was divided into dosing site and peripheral tissue. Perfusate and all tissue samples were combusted in an automated tissue oxidizer.


ANALYSIS
- Method type(s) for identification: Liquid scintillation counting (Packard Chemical Co., Downers Grove, IL)
Details on in vitro test system (if applicable):
SKIN PREPARATION
- Type of skin: From pig
- Thickness of skin (in mm): 0.5
- Justification of species, anatomical site and preparative technique:The studies were conducted in an ex vivo perfused porcine skin model that has been shown to predict human exposure because of its intact vasculature, as well as anatomical and physiological similarities to human skin

PRINCIPLES OF ASSAY
- Diffusion cell: Teflon diffusion cell blocks
- Receptor fluid: Krebs–ringer bicarbonate buffer with added glucose and bovine serum albumin
- Flow-through system: Yes (flow rate: 4.0 ml/h)
- Test temperature: 37 degree C
- Humidity: 55-65%
- Occlusion: Nonoccluded

Results and discussion

Signs and symptoms of toxicity:
not examined
Dermal irritation:
not examined
Absorption in different matrices:
- Absorption:
IPPSF: (%) 0.10 ± 0.04; (µg) 0.96 ± 0.37
PSFT: (%) 0.14 ± 0.02
- Surface swabs:
IPPSF: (%) 77.61 ± 2.68; (µg) 735.60 ± 23.90
PSFT: (%) 78.40 ± 5.00
- Stratum corneum (in vitro test system):
IPPSF: (%) 0.90 ± 0.33; (µg) 8.56 ± 3.07
PSFT: (%) 2.21 ± 0.39
- Dosed skin:
IPPSF: (%) 0.32 ± 0.04; (µg) 2.99 ± 0.42
PSFT: (%) 0.41 ± 0.13
- Penetration:
IPPSF: (%) 0.75 ± 0.21; (µg) 7.16 ± 2.03
PSFT: (%) 2.76 ± 0.51
Total recovery:
- Total recovery:
IPPSF: (%) 84.38 ± 1.52; (µg) 799.80 ± 12.70
PSFT: (%) 91.76 ± 4.92
Conversion factor human vs. animal skin:
Not determined

Any other information on results incl. tables

The amount of applied chemical that penetrates the stratum corneum and skin in the IPPSF is considered to be the maximum estimate in humans that ultimately could be absorbed since it assumes no loss due to exfoliation of the stratum corneum.

Comparison of the IPPSF results with those from previous studies indicates that the amounts absorbed into the perfusate are remarkably similar, although a smaller percentage of the applied dose penetrated into the IPPSF.

The mean perfusate flux in the IPPSF and PSFT studies are presented in Figure 2 and 3.

Applicant's summary and conclusion

Conclusions:
Under the test conditions, nonylphenol was considered to be minimally absorbed in the IPPSF model and the potential systematic exposure from skin contact in humans is considerably less than 1%. According to the author this result confirms the estimates from previous in vitro studies.
Executive summary:

A study was conducted to evaluate the absorption of the test substance in isolated perfused skin (IPPSF) and to assess the percutaneous absorption to a previous published in vitro porcine study in a flow-through diffusion cell system (PSFT).

The isolated perfused porcine skin flap (IPPSF), created on the porcine ventral abdomen, was used in this study. Two single-pedicle axial pattern skin flaps, each lateral to the ventral midline on the pig abdomen, were created during stage 1 and harvested during stage 2 surgery. The flaps were cannulated, flushed to clear the vasculature of blood, and transferred to a perfusion chamber. The flaps were perfused for 1 h prior to dosing, during which arterial and venous samples were collected to determine glucose utilization and zero-time perfusate samples for flux determinations. A stomahesive template was secured to the flap with skin-bond. The skin flap was returned to the chamber and dosed with radiolabeled test substance and after the perfusion was resumed. Perfusate samples were later collected and analyzed for glucose and radioactivity.The remaining venous efflux was collected for 14C determination. The flap and cradle were removed from the flap chamber and rinsed for recovery and the dose area was washed. The tape strips were placed in vials containing ethyl acetate for estimation of stratum corneum penetration.

Flow-through diffusion cell system (PSFT): Pig skin was dermatomed and circular sections were mounted epidermal side up in diffusion cell blocks. Skin was equilibrated in the diffusion cell chambers prior to dosing. A constant perfusate flow rate was maintained during the study. Treatments were dosed with test substance to a nonoccluded areal and perfusate was collected during the study. At the completion of the study tape strips were collected for estimation of stratum corneum penetration. The upper half of the chamber was rinsed and the wash collected for mass balance determination. The remaining skin section was divided into dosing site and peripheral tissue. Perfusate and all tissue samples were then analyzed for total 14C determination.

The amount of applied chemical that penetrates the stratum corneum and skin in the IPPSF is considered to be the maximum estimate in humans that ultimately could be absorbed since it assumes no loss due to exfoliation of the stratum corneum.

Comparison of the IPPSF results with those from previous studies indicates that the amounts absorbed into the perfusate are remarkably similar, although a smaller percentage of the applied dose penetrated into the IPPSF.

Under the study conditions, the test substance was considered to be minimally absorbed in the IPPSF model and the potential systematic exposure from skin contact in humans is considerably less than 1%. According to the author this result confirms the estimates from previous in vitro studies.