Registration Dossier

Administrative data

Endpoint:
dermal absorption in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was reported in a peer-reviewed journal without GLP compliance.

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2000
Report date:
1999

Materials and methods

Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
Penetration of the test substance as measured by diffusion cell through rat, mouse and human skin samples with detection by Liquid Snitillation counting and HPLC analysis.
GLP compliance:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
2,3-epoxypropyl o-tolyl ether
EC Number:
218-645-3
EC Name:
2,3-epoxypropyl o-tolyl ether
Cas Number:
2210-79-9
Molecular formula:
C10H12O2
IUPAC Name:
2-[(2-methylphenoxy)methyl]oxirane
Constituent 2
Reference substance name:
Oxirane, 2-[(2-methylphenoxy)methyl]-
IUPAC Name:
Oxirane, 2-[(2-methylphenoxy)methyl]-
Constituent 3
Reference substance name:
o-Cresyl glycidyl ether (o-CGE).
IUPAC Name:
o-Cresyl glycidyl ether (o-CGE).
Test material form:
other: Liquid at room temperature.
Details on test material:
As per IUCLID5 Sections 1.1, 1.2, 1.3 and the publication.
Radiolabelling:
yes

Test animals

Species:
other: Rat, mouse and human skin samples
Strain:
other: Fisher 344 rats and C3H mice
Sex:
male/female
Details on test animals or test system and environmental conditions:
Male Fisher 344 rats (~ 250 gm) and male C3H mice (~ 25 gm) were from the Central Laboratories for the Blood Banks (CLB) (Amsterdam, The Netherlands). Animals were kept on a 12 h light/dark cycle in humidity- (60±15% relative humidity) and temperature- (22±2 °C) controlled mass-air-displacement rooms. A standard rodent diet (VRF-I, Broekman Institunt [Charles Rivet Laboratories], Someren, The Netherlands) and de—ionized water were supplied ad libitum. Following an acclimation of 1 week, the animals were used as the source for viable rodent skin. Fresh full-thickness healthy human breast skin was from five female Caucasian patients, aged 17-41.

Administration / exposure

Type of coverage:
other: Open and occluded.
Vehicle:
acetone
Duration of exposure:
24 hr.
Doses:
~ 635 mM.
No. of animals per group:
There were 3-4 diffusion cells per skin sample.
Control animals:
no
Details on study design:
The skin samples were mounted, epidermis uppermost, in a flow-through diffusion cell system. . The system consisted of (1) 12 stainless steel diffusion cells, which were stirred continuously with magnetic stirrer bars (Variomag HP 15 Multipoint, HP Labortechnik, Munich, Germany) to prevent irregular penetration due to air bubbles underneath the skin membrane, (2) a fraction collector holding 20 ml glass scintillation vials, (3) a thermostatically controlled water circulator (PolyScience, USA) to heat the jackets holding the cells in such a way that the skin surface temperature was kept at 12± 1 °C, and (4) a cassette peristaltic pump (Watson Marlow, Falmouth, UK). The exposed skin surface was ~ 0.635 cm2. The underside of the skin was exposed to continuously flowing (flow rate 1.5 ml/h) receptor fluid consisting of Hanks’ balanced salt solution, without phenol red and sodium bicarbonate, buffered with 25 mM HEPES (pH 7.40) and containing 2.5% v/v BSA and 50 ug gentamicin per ml. The receptor fluid was transported to the cells and from the cells, through the pump, to the fraction collector through PVC tubing (Accurated tubing, Elkay). In some experiments the cells were occluded by placing a polycarbonate lid over the cells.
Details on in vitro test system (if applicable):
Three different skin donors (both for human and rodent skin) were used for each of the study Human skin was dissected from the tissue removed during mammoplastic reduction surgery using a scalpel and cleaned with physiological saline. The shaved area from the rodent skin was cut out with dissecting scissors. Excess subcutaneous tissue was removed front the skin samples with a scalpel. The skin was placed on a Teflon dissecting board and full-thickness skin circles were cut out using a circular sharpened steel cutter. Mouse skin was always used at full thickness since it is so thin that it can not be derniatomed. Human and rat skin was only used following dermatomization. The skin, epidermis up, was stretched over a small band of Teflon and a sheet of skin was cut off using a hand-held keratotome (Storz Instrument Co., US). Skin circles were cut out of this sheet using small dissection scissors. The gross integrity of the skin was assessed visually.

In the experiment, which was carried out in triplicate, three-to-four diffusion cells with skin from the same donor (human or animal) were used to study the penetration of each of o-CGE. Aliquots of 5.0 ul o-CGE dissolved in acetone at a concentration of ~ 635 mM were applied to the exposed skin surface using a niicropipette (final concentration 5.0 umol/cm2). The receptor fluid was collected in 3-hourly fractions for 24 h following application of the test substance. The fractions-were weighed for determination of the actual flow rates and the radioactivity in an aliquot of the fractions was determined by LSC. The remaining portions of the collected fractions were extracted twice with a double volume of ethyl acetate. An aliquot of DMSO was added to the combined fractions and a gentle stream of nitrogen evaporated the ethyl acetate. The DMSO residue was mixed with an equal volume of methanol and subsequently analysed by HPLC with radiodetection.

Results and discussion

Signs and symptoms of toxicity:
not specified
Remarks:
The test system was in vitro skin.
Dermal irritation:
not specified
Remarks:
The test system was in vitro skin.
Total recovery:
13 +/- 3 to 26 +/- 5%.

Any other information on results incl. tables

With o-CGE, the dermal penetration reached a plateau at absorption of ~ 10, 18 and 23 % of the applied dose with human, rat and mouse skin respectively. In all three cases, the curves started levelling off after ~ 12 hr. Occlusion of the skin significantly enhanced the dermal penetration of o-CGE through human, rat as well as mouse skin: the percentage of the applied dose that had penetrated through the skin was roughly doubled by occlusion. Based upon absorption rate constant human skin was 1.4 -2 -fold less permeable to o-CGE.

For o-CGE, a considerable amount of the penetrated dose (86—88 %), was hydrolysed to mephenesin (the glycerol ether of o-cresol) during the first hours of penetration in human, rat as well as mouse skin, but as the study progressed less o-CGE was hydrolysed and more unchanged compound was recovered from the receptor fluid. Little or no diol was detected.

Applicant's summary and conclusion

Conclusions:
Only approximately 10-22% of the applied dose of o-CGE (2,3-epoxypropyl o-tolyl ether ) penetrated the skin samples. Furthermore total recovery was 13-26%. The low perneability and recovery of o-CGE is believed to be due to its volatility. Occlusion of the diffusion cells resulted in an approximately doubling of the precent absorption.

Approximately 86-88% of the penetrated dose of o-CGE was hydrolysed to mephenesin (the glycerol ether of o-cresol) during the first hours of penetration in human, rat as well as mouse skin.
Executive summary:

The test substance, 2,3-epoxypropylo-tolyl ether ( o-Cresyl glycidyl ether/o-CGE) was assessed for dermal penetration in vitro in diffusion cells with human, rat and mouse skin samples. Only approximately 10-22% of the applied dose of o-CGE (2,3-epoxypropyl o-tolyl ether ) penetrated the skin samples. Furthermore, total recovery was only13-26%. The low perneability and recovery of o-CGE is believed to be due to its volatility. Occlusion of the diffusion cells resulted in an approximately doubling of the precent absorption. Approximately 86-88% of the penetrated dose of o-CGE was hydrolysed to mephenesin (the glycerol ether of o-cresol) during the first hours of penetration in human, rat as well as mouse skin.