IMMUNOHISTOCHEMICAL AND ULTRASTRUCTURAL STUDY OF THE STRIATED DUCTS OF THE SUBMANDIBULAR AND SUBLINGUAL SALIVARY GLANDS OF ALBINO RAT

The striated ducts of the salivary glands of many mammalian species engage in secretion of organic products in addition to their role in electrolyte homeostasis (Tandler and Phillip, 2000). They are the major site of modification of the electrolyte content of the primary saliva. Na~ and cr are reabsorbed and K~ and HC03- are secreted, with a net reduction in tonicity of the saliva (Hand, 1979; Roussa et al., 199B). The organic products include Kallikrein and may be some growth factors, vasoactive substances and digestive enzymes (Tandler and Phillip, 2000). The resorption and secretion in exocrine glands have been related to 8100 proteins (Lauboeck and Egerbacher, 1997). 8-100 is a group of closely related, small, acidic Ca2+-binding proteins (8-100aO, 8-100a and 8-1OOb). It is structurally related to calmodulin and other Ca2+-binding proteins (Donato, 1986). S100 proteins have no known enzymatic activity and exert their intracellular effects via interaction with and regulation of the activity of other proteins, termed target proteins, in both a Ca(2+)-dependent and Ca(2+)-independent manner (Zimmer et aI., 2003). A unique feature of these proteins is that individual members are localized in specific cellular compartments from which some are able to relocate upon Ca2+ activation, transducing the Ca2+ signal in a temporal and spacial manner by interacting with different targets specific for each 8100 protein (Heizmann et aI., 2002).Within cells, 8-100 proteins have been reported to regulate proteinphosphorylation, ATPase, adenylate cyclase, and aldolase activities, the dynamics of cytoskeleton components, transcription factors, Ca(2+) homeostasis, and cell proliferation and differentiation (Donato, 1991, 1999,2001).