Epidermal water permeation in vertebrates: an in vitro study using tritiated water.

Structural lipids play an important role in the water holding property of the skin. beta emitters are known to pass through the skin barrier. A permeability cell was constructed and tritiated water was used to determine the rate of in vitro water permeation through the epidermis. The epidermal sheets from different classes of vertebrates were compared for water permeation. Some of the samples were treated with solvents, surfactants and conditioners, to fathom permeability changes of the epidermis after these treatments, at various time intervals. Solvent treated epidermal sheets show very high degree of permeation, both in rat pup skin and pigeon skin. Glycerol, Brij 99 and beewax treated skin shows negligible permeation; or rather, helps in retention of water compared to normal and solvent treated skin. Comparison of water permeation in rat, pigeon and lizard skin shows that the reptilian integument is more efficient, as it allows very less permeation of water compared to the avian and mammalian epidermis. These observations suggest that tritiated water could be used for determining in vitro water permeation through the epidermis.