Diffusion barriers in skin--a new method of comparison.

Area of Science:

• Pharmacology
• Dermatology
• Biophysics

Background:

• The skin acts as a primary barrier against xenobiotic penetration.
• Understanding differential skin barrier properties is crucial for drug delivery and toxicology.
• Nandrolone and allyl oestrenol are anabolic steroids with varying lipophilicity.

Purpose of the Study:

• To compare the skin barrier potential to nandrolone and allyl oestrenol penetration across species.
• To quantify the barrier contribution of different skin layers in humans.
• To establish a quantitative measure of skin barrier function using 'penetration half-life'.

Main Methods:

• Quantification of skin barrier potential using a 'penetration half-life' method.
• Comparative analysis of nandrolone and allyl oestrenol penetration in human, rat, and hamster skin.
• Assessment of barrier function across distinct human skin layers (stratum corneum, dermis).

Main Results:

• Skin barrier strength ranking: human = haired rat ≥ hairless rat > hairless hamster.
• The stratum corneum and dermis exhibit comparable barrier effectiveness in human skin.
• The dermis demonstrates a significant, though slightly lesser, barrier effect than the stratum corneum.

Conclusions:

• Human skin possesses a robust barrier to nandrolone and allyl oestrenol, similar to haired rats.
• The dermis is a critical component of the overall skin barrier, not solely the stratum corneum.
• The 'penetration half-life' method provides a valuable tool for assessing skin barrier properties.