A POLARIZED SALIVARY CELL MONOLAYER USEFUL FOR STUDYING TRANSEPITHELIAL FLUID MOVEMENT IN-VITRO

There are no reported, convenient in vitro models for studying polariz ed functions in salivary epithelial cells. Accordingly, we examined th ree often-used salivary cell lines for their ability to form a polariz ed monolayer on permeable, collagen-coated polycarbonate filters. Only the SMIE line, derived from rat submandibular gland, had this ability . The SMIE cell monolayer exhibited junctional complexes, with a tight -junction-associated protein, ZO-1, localized to cell-cell contact are as. The Na+/K+-ATPase alpha(1)-subunit was detected predominantly in t he basolateral membranes, while the Na+/H+ exchanger isoform 2 appeare d primarily in the apical membranes. Using adenovirus-mediated cDNA tr ansfer, SMIE cells were shown to be capable of routing marker proteins (beta-galactosidase +/- nuclear targeting signal, alpha(1)-antitrypsi n, aquaporin-1) to appropriate locations. Furthermore, this salivary c ell monolayer provided a convenient tool for studying aquaporin-1-medi ated, osmotically directed, transepithelial fluid movement in vitro. T hus, SMIE cells appear to be a useful experimental model with which to study some polarized functions in a salivary epithelial cell line.