Specimens from four regions of oral mucosa (palate, buccal mucosa, lateral border of the tongue, and the floor of the mouth) and of abdominal skin were taken from 58 individuals at autopsy, for determination of permeability constants (Kp) to tritium-labeled water. Comparisons between fresh specimens and those stored at -80 degrees C revealed no significant effect on Kp as a result of freezing; similar results were found with use of specimens from corresponding regions of the pig. Values for Kp were significantly different for all of the tissue regions examined and ranged from 44 +/- 4 x 10(-7) cm/min for skin to 973 +/- 33 x 10(-7) cm/min for the floor of the mouth, which was the most permeable region. Similar differences were evident among corresponding regions of porcine oral mucosa and skin. Moreover, the Kp values obtained for human tissues were not significantly different from those of the pig, except for the floor of the mouth, which was more permeable in human than in pig tissue. The results reveal interesting differences in the permeability of human oral mucosa that might be related to susceptibility to mucosal disease in those conditions where local extrinsic etiological agents are implicated.

These results suggest that short-term exposure to ethanol may act as a permeability enhancer, possibly by causing molecular rearrangement of the permeability barrier, not as a result of lipid extraction.

ABSTRACT:In discussing permeability, we are describing one of the fundamental barrier functions of oral mucosa. Despite assumptions to the contrary, the oral mucosa is not a uniformly, highly permeable tissue like gut, but shows regional variation. The keratinized areas, such as gingiva and hard palate, are least permeable and nonkeratinized lining areas are most permeable. This variation appears to reflect differences in the types of lipid making up the intercellular permeability barrier in the superficial layers of the epithelium. Differences in permeability may be related to regional differences in the prevalence of certain mucosal diseases and can be utilized to advantage for local and systemic drug delivery.

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