Topographical distribution of cells in the rat submandibular gland duct system with special reference to dark cells and tuft cells

Abstract

The duct system of the rat submandibular gland consists of the intercalated duct, the granular convoluted tubule, the striated duct, the excretory duct, the main excretory duct, and the salivary bladder. The duct system contains special cell types, such as dark cells and tuft cells, in addition to principal cells. However, little is known about cell distribution in the duct system. The purpose of the present study was to examine cell distribution and to perform a morphometric analysis of the duct system. Transmission and scanning electron microscopy were used to examine the duct system of the rat submandibular gland. Six regions in the duct system, the striated duct, the interlobular excretory duct, the 5-mm proximal excretory duct from the hilus, the main excretory duct at the hilus, the 10-mm distal main excretory duct from the hilus, and the salivary bladder, were investigated. Morphometric and statistical analyses of the data were then performed. The epithelium of the duct system consisted of a heterogeneous cell population. Dark cells and tuft cells were present throughout the duct system. The principal, dark, and tuft cells were distinguished by their different microvilli by using a scanning electron microscope. The frequency of these cells in the total epithelial cell population was as follows: The percentage of principal cells in the six regions of the duct system varied from 87.5% to 94.4%, that of dark cells varied from 4.1% to 7.2%, and that of tuft cells varied from 1.8% to 7.2%. The number of principal and tuft cells was significantly different between the striated duct and the main excretory duct at the hilus (P Ͻ 0.01). However, no significant difference in number of dark cells throughout the duct system was observed (P Ͼ 0.05). The abundance of the principal, dark, and tuft cells in the duct system of the rat submandibular gland was determined. Few tuft cells were distributed in the striated duct, and most were found at the hilus. Dark cells were distributed equally throughout the duct system. Anat. Rec. 252:159-164, 1998.

Tuft cells

“…Sbarbati and Osculati (2005) have recently carried out an extensive survey of the same cell type referred to as brush cells. In the digestive tract, tuft cells are present in the salivary duct (Shackleford & Schneyer, 1971;Sato, 1980Sato, , 1982Hand, 1981;Sato & Miyoshi, 1988;Higashi et al, 1989;Sato & Miyoshi, 1996, 1998aSato et al, 1998Sato et al, , 2000Sato et al, , 2002Sato et al, , 2004, stomach (Hammond & LaDeur, 1968;Isomäki, 1973;Wattel & Geuze, 1978;Luciano et al, 1980;Luciano & Real, 1992;Luciano et al, 1993;Kugler et al, 1994;Luciano et al, 2003), gallbladder (Luciano & Real, 1969, 1990Nevalainen, 1977;Luciano et al, 1981), common bile duct (Riches, 1972;Luciano et al, 1981;Iseki, 1991), small and (Trier, 1963;Silva, 1966;Schofield, 1970;Nabeyama & Leblond, 1974;Tsubouchi & Leblond, 1979;Sugimoto et al, 1983;Trier et al, 1987;Gebhard & Gebert, 1999;Wille, 2001), and pancreatic duct (Weyrauch & Schnorr, 1976;Kugler et al, 1994;. Such cells have also been repo...…”

“…Tuft cells are present in the hollow organs of the digestive and respiratory tracts including the duct system of the salivary gland (Sato & Miyoshi, 1998a). They are characterized by long and blunt microvilli with prominent rootlets and by a well-developed tubulovesicular system in the supranuclear cytoplasm.…”

Secretion by striated ducts of mammalian major salivary glands: Review from an ultrastructural, functional, and evolutionary perspective

“…1). In the rat submandibular gland, they constitute ∼4.8% of the duct wall (Sato and Miyoshi, 1998). The dark cells usually are narrow and contain an electron‐dense cytoplasm in which the basic organelles are sparse.…”

“…The apical cytoplasm of SD cells in salivary glands of many species contains numerous small, ‘empty’‐appearing vesicles (Fig. 3A–C) [although in the rat submandibular gland they may contain fine filaments (Sato and Miyoshi,1998)]; a variety of functions has been suggested for them. By using tritium‐labeled fucose, (Hand 1979, 1987) demonstrated that at least some of these vesicles are involved in the transport of polysaccharides to the glycocalyx coating the apical surface of the duct cells and of membrane components to be incorporated into the apical plasmalemma.…”

Interlobular excretory ducts of mammalian salivary glands: Structural and histochemical review

“…14) (Tandler et al, 1997c). Dark cells constitute 4.7% of the cells in the wall of the proximal EDs in the rat submandibular gland and 7.2% of the cells in the more distal EDs (Sato and Miyoshi, 1998). The nature of dark cells is unclear.…”