Initial characterization of the proteins of keratinized epithelium of rat oral mucosa

Abstract

Rat cheek and palate epithelium, representing the least and most keratinized portions of the oral mucosa, were compared by biochemical and immunologic methods. Immunofluorescence using antibody to the epidermal fibrous proteins showed a positive reaction in the keratohyalin granules in cheek, palate and epidermis. A mild reaction was detectable in the stratum corneum of cheek and palate in contrast to the intense reaction of the epidermal stratum corneum, suggesting that antigenic sites in the oral epithelium differ or are blocked in situ. Proteins were extracted from the stratum corneum by detergent, urea and reducing agents and were compared to those of stratum corneum of newborn rat epidermis by sodium dodecyl sulphate (NaDS) polyacrylamide gel electrophoresis. Amino acid compositions of partially purified proteins of the stratum corneum of cheek and palate epithelium were very similar and to the fibrous proteins of epidermis. All these oral proteins cross-reacted with antibody to epidermal fibrous protein. The third major protein from rat epidermis which had a high content of arginine and histidine was not detected in extracts of the oral stratum corneum.