GIANT SECRETORY GRANULES IN THE DUCTS OF THE PAROTID AND SUBMANDIBULAR GLANDS OF THE SLOW LORIS

The parotid and submandibular glands of a slow loris, a rare Southeast Asian primate, were obtained after the head had been perfused by fixa tive for a study of the brain, These tissues were processed by convent ional means for electron microscopy. Glands also were obtained at auto psy from 2 other lorises, fixed by immersion in formalin, and subjecte d to a battery of tests for glycoconjugates. In the parotid gland, a s hort segment of the proximal striated duct lacks both basal striations and any sign of secretory activity, The major portion of the striated duct consists of tall cells that contain a spectrum of secretory gran ules, some larger than the nuclei (many granules are > 9 mu m in diame ter), These granules, which are delimited by a single membrane, are ca pable of chain exocytosis. Many of the giant granules have bundles of cytofilaments (4.5-6.5 nm) in apparent association with their surface, Occasional cells contain numerous small granules. Duct cells with or without granules lack basal striations. The granules contain neutral g lycoconjugates but no acidic glycoconjugates. Some, but not all, inter lobular excretory ducts also have secretory granules that run the gamu t from tiny to giant, Exactly the same situation occurs in the submand ibular gland. Unlike other primates, which may have duct cells that co ntain only a few tiny granules in their apices, the cells in both the striated and excretory ducts in the slow loris appear to be specialize d for secretion rather than for transport, The biofunction of the gian t granules is unknown.