Thermotropic Effects on Skin Permeability.

Abstract

The present study relates thermally induced changes in the microscopic phases of the horny structure of hairless mouse skin to increased permeability of this skin resulting from thermal trauma as measured in in vitro diffusion cells. The permeability coefficients (mass transfer coefficients) of phenol paired with methanol and of neomycin-(beta) paired with ethanol, in each case the alkanol acting as a reference, have been characterized in aqueous media for skins burned on hot water and metal surface at varied temperatures and for varied times. Results have been compared with the permeability of untreated skin sections and sections stripped of their stratum corneum or otherwise processed. For all compounds studied marked increases in permeability coefficients are seen past a critical temperature, which is 75(DEGREES)C for the low molecular weight alkanols and phenol but is 90(DEGREES)C for neomycin-(beta). Very harsh burning conditions destroy the stratum corneum's unique ability to regulate mass transfer. The data suggest specific thermally induced phase transitions in the skin's horny element open to skin to diffusion of these species. Complimentary studies of thermotropic effects in skin were accomplished using differential scanning calorimetry (DSC). The most telling thermograms were those on stratum corneum isolated from skin sections which had been burned on the br and ing device for different durations at a given temperature (100(DEGREES)C) or for fixed durations (10 sec and 60 sec) at increasing temperatures. Systematic shifts in these curves suggest a progressive denaturation of the keratin component of the tissue is responsible for its lost barrier property. On the other h and , the fusion of lipids appears to be a reversible process largely unrelated to barrier alteration. The clinical significance of the observed thermotropic effects is considered.