Effect of enzyme digestion on the permeability barrier in keratinizing and non-keratinizing epithelia.

In an attempt to characterize the permeability barrier of the oral mucosa and skin, small pieces of keratinized and non-keratinized oral epithelia and epidermis were digested with specific enzymes. These enzymes were selected for their effect on carbohydrate-protein, or carbohydrate-lipid compounds and phospholipids. The effect of the enzyme treatment was monitored by exposing the digested tissue to horseradish peroxidase. Electron microscopic examination of tissue treated with phospholipases revealed considerable damage to membrane structures but not to the integrity of the permeability barrier. Hyaluronidase and neuraminidase caused less structural damage but did not impair barrier function; this was only seen after treatment with chondroitinase ABC. This enzyme may degrade certain of the polar molecules thought to be necessary to stabilize the neutral lipid bilayers of the intercellular barrier and thus disrupt its barrier properties.