Analysis of changes in the expression pattern of claudins using salivary acinar cells in primary culture.

Primary saliva is produced from blood plasma in the acini of salivary glands and is modified by ion adsorption and secretion as the saliva passes through the ducts. In rodents, acinar cells of salivary glands express claudin-3 but not claudin-4, whereas duct cells express both claudins-3 and -4. The distinct claudin expression patterns may reflect differences in the permeability of tight junctions between acinar and duct cells. To analyze the role of claudins in salivary glands, we established a system for the primary culture of parotid acinar cells, where the expression patterns of claudins are remarkably changed. Real-time RT-PCR and immunoblot analyses reveal that the expression levels of claudins-4 and -6 increased, whereas claudins-3 and -10 decreased. We found that the signal to induce those changes is triggered during cell isolation and is mediated by Src and p38 MAP kinase. Here, we introduce the methods used to determine the signal pathway that induces the change in claudin expression.