The Water Barrier in Human Epidermis

Abstract

The rate of water vapor transpiration through normal excised human skin at 10 to 20 C is 2.9 gm/sq m/hr, with a standard deviation of 1.9 gm/sq m/hr.

The rate of water vapor transpiration through excised skin is not affected by freezedrying, rapid freezing in 15% glycerol solution to 68 C, exposure to 0.1 normal sodium hydroxide or to 6 M urea for 24 hours, or exposure to boiling water or flaming benzene so long as the stratum corneum is not visibly physically disrupted.

Stratum corneum, with an intact water vapor barrier, can be separated from the cellular epidermis by digestion of skin for 24 hours with 3% trypsin at 37 C. Stratum corneum so separated has no identifiable basal layers.

Extraction with ether for 8 or 24 hours increases the rate of cutaneous transpiration of water vapor fourfold to ninefold.

Extraction of excised human skin with acetone for 3 hours, followed by extraction with hexane for 8 hours, removes its water vapor barrier properties and increases the rate of transpiration 75-fold.

Replacing the substances removed by acetone-hexane extraction onto the surface of the acetone-hexane extracted, water-vapor-barrier-lacking skin almost completely restores the water vapor barrier to normal, indicating that the physical structural characteristics of the epidermis have little to do with maintenance of the water vapor barrier.

A theoretical scheme of the physical-chemical nature of the water vapor barrier, based on our observations, and on previous data, is presented.

This water vapor barrier complex in the stratum corneum is about 98% efficient. Water vapor moved through skin having an intact barrier at the rate of 2.9±1.9 gm/ sq m/hr with temperatures varying between 10 and 20 C, while it moved through barrierdeficient skin at the rate of 229±81 gm/ sq m/hr at the same temperatures.