Autoradiographic study of the penetration of radiolabelled dextrans and inulin through non‐keratinized oral mucosain vitro

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Abstract
Although a well known barrier effect against the penetration of macromolecules exists at the basement membrane region of epithelial tissues, recent reports suggest that the penetration of smaller molecules may also be impeded by this region. Considering the probable importance of the permeability of gingival crevicular tissues in the etiology of inflammatory periodontal disease, the present study was designed to evaluate the barrier function of the basement membrane region of non‐keratinized oral mucosal epithelium to a series of radiolabelled penetrating molecules of increasing molecular weight. Tritium labeled inulin (ℳ 5,000), dextran 20 (ℳ 20,000) and dextran 70 (ℳ 70,000) were used as penetrating molecules, and autoradiographic tracer techniques were used to evaluate the barrier function. The study was conducted in vitro to eliminate vascular “wash‐out” effects and to facilitate study of penetration across the basement membrane region in both directions. The results indicated that although the penetration of inulin and dextran 70 was impeded by the basement membrane region, the penetration of dextran 20 was not affected. Therefore, the barrier function of the basement membrane region is not solely dependent on the molecular weight of the penetration molecule. Mechanisms to account for the findings are described and the significance to periodontal disease is discussed.