Cultured buccal epithelium: an in vitro model derived from the hamster pouch for studying drug transport and metabolism.

Hamster pouch buccal epithelium (HPBE) was isolated and grown in primary cultures on rat-tail collagen-coated growth surfaces. The cultured pouch buccal epithelium (CPBE) was characterized morphologically with electron microscopy as stratified multilayers of epithelial cells with well-developed tonofibrillar-desmosomal complexes. Only the superficial layer of the cultured cells exhibited evidence of terminal differentiation. Alkaline phosphatase, alcohol dehydrogenase, and aminopeptidase activities in the primary cultured cells were determined by biochemical assays and found to be similar to those of homogenates of freshly excised hamster pouch epithelium. In addition, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS PAGE), keratins and total proteins associated with the cultured cells were similar to those of freshly excised HPBE. The permeability characteristics of the cultured cells was determined by placing cultured cells grown on permeable polycarbonate disks in a Side-Bi-Side diffusion apparatus and quantitating the transcellular flux of tritium-labeled water, fluorescein, and fluorescein isothiocyanate dextrans (MW 3800 to 150,000). The cultured cells were least permeable on the third day of culture and were not permeable to substances with a MW greater than about 18,000. Our results indicate that primary cultures of hamster pouch epithelium exhibit biochemical properties similar to those of the excised hamster pouch epithelium from which they were derived. The morphological and permeability characteristics of cultured hamster epithelium were similar to those of nonkeratinized stratified oral epithelia typical of buccal mucosa in man, rabbit, and other species. CPBE, as described here, represents a potentially useful tool for in vitro drug transport, metabolism, pharmacology, and toxicology studies.