Ultrastructure of the Parotid Salivary Gland in the Greater Cane Rats (Thryonomys Swinderianus)

The parotid glands of adult male African greater cane rat (Thryonomys swinderianus) were examined by light microscopy (semi-thin sections) and transmission electron microscopy. Histologically, it consisted of acinar cells with vacuoles which corresponded to large oval electron-dense granules, intercalated, striated ducts, and myoepithelial cells which contacted the cells and intercalated ducts (IDs). The cytoplasmic organizations of acinar cells represented the features of serous secreting cells. Ultrastructurally, the acinar cells contained granules of low and moderately electron densities without substructures in their matrix. Lipid droplets were interspersed with the granules. Several coalesced low electron-dense granules were common in some of the acinar cells. The acinar cells also contained few dilated (vesicular) and abundant parallel arrays of tubular rough endoplasmic reticulum and extensive Golgi complex. IDs were lined by tall cuboidal cells interconnected by tight junctions. Secretory granules were absent in their cytoplasm. Striated ducts were composed of columnar cells with few basal cells, and secretory granules were absent as well. Apical blebbing was observed in these ducts. Myoepithelial cells were limited to the acinar-intercalated ductal system. Nerve terminals were observed among the adjacent acinar cells and the underlying basement lamina. The functional significance of these structures is discussed.