Organ Cell Biology of Salivary Secretion: Integrated analyses by combined approaches

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An organ is a mass of diverse cells possessing various morphological and functional identities, yet it can behave as an integrated unity. This study was aimed to clarify the structural bases that ensure organs to acquire the harmonized function. Salivary gland function is primarily achieved by the compartmentalized epithelial domains, acini and ducts, which also exhibit characteristic morphological specialization. High-speed confocal microscopy showed distinct pattern of calcium signaling between acini and ducts. Cells in acini responded synchronously while those in ducts responded asynchronously. A gap junction molecule, connexin 32, was immunolocalized predominantly between the acinar cells; thus the calcium signaling system in salivary glands is constructed specifically according to the tissue architecture. Beta-galactosidase knock-out mice revealed the appearance of vacuolar structures in the acinar domain and the granulated duct domain. A rat with hypothyroydism, rdw, exhibited the lack of the granulated duct segment. Beta-galactosidase and thyroxine are considered to play significant roles in the morphogenesis of acinar and duct segments. I was concluded that the segment specific differentiation of epithelia plays fundamental roles in controlling the harmonized organ function.