Abstract
Tight junction is the essential structure for salivary epithelial cells to keep polarity and to secrete fluid unidirectionally. Previously, we established a system for primary culture of parotid acinar cells. Acinar cells isolated from the rat parotid glands formed large colonies and attached to the basement of dishes at 24 h after the dispersion. After 2 days, most cells spread as a monolayer whereas a part of cells formed hemispherical lumps. Analysis with electron microscopy suggests that cells in the lumps retained original tight junctions and lumens. On the other hand, cells in monolayer also formed tight junctions. Immunofluorescence microscopy showed claudin-1 was observed in the lumps, while claudin-4 was detected at the tight junctions in monolayer. Most cells in the monolayer that had claudin-4-positive tight junctions retained secretory granules containing amylase. Therefore, the claudin-4-positive cells were probably derived from acinar cells, but not from ductal cells. Immunoblotting analysis showed that claudin-4 was expressed at 24 h and its expression increased time-dependently during the culture, although it was not detected just after the dispersion. These results suggest that the expression of claudins changed from isotype 1 to 4 while the morphology of the acinar cells changed to monolayer. Claudins possibly have a correlation with the formation and maintenance of culture configuration in parotid acinar cells. [J Physiol Sci. 2006;56 Suppl:S110]
