Morphology and cytochemistry of acinar secretory granules in normal and isoproterenol‐treated rat submandibular glands

Abstract

Several fixation procedures have been utilized in a fine-structural study of rat submandibular glands with the aim of correlating the morphology of granule substructure with its composition. Procedures included fixation with aldehyde in a variety of buffers, with or without fixation additives such as tannic acid or calcium chloride. Both immersion and perfusion fixation studies were performed. Osmium tetroxide postfixed tissue was compared with non-postfixed tissue. Thin sections were stained for carbohydrate-containing constituents by either periodic acid-thiocarbohydrazide-silver proteinate or tannic acid-ferric chloride sequences. The morphology and cytochemistry of acinar secretory granules were highly dependent upon the fixation procedure utilized. In postfixed tissue, fine filaments and vesicles were the major granule constituents. Filaments often aggregated into fibrils in fixatives containing phosphate buffer or calcium, whereas vesicles were prominent with fixatives containing collidine buffer. Tannic acid, as a fixation additive, imparted enhanced density to the peripheral rim of aggregated filaments. If post fixation was eliminated, an amorphous meshlike material was the major granule component. This stained readily with methods for carbohydrate whereas the granules of post-osmicated tissue did not. Following chronic isoproterenol treatment the degree of filament aggregation in postfixed tissue was augmented, and this corresponded to an increase in amount of material stainable for carbohydrate in non-post-osmicated tissue.

Scanning Electron Microscopy of Human Submandibular Gland

“…Although TEM studies of human SBM glands have accurately de scribed the detailed morphological appearance of the secretory granules [6], observations by SEM provided a view of the u'hole granules, thus adding knowledge of their actual shape, size, and distribution. Although fixa tion modifies the structure of secretory granules [15], studies with SEM applied to rat salivary glands showed that serous acini (parotid gland) were loaded with spher ical granules [16], just as was observed in the human submandibular glands. The method we used demon strated that it is useful for the observation of serous material.…”

Mitosis and Hypertrophy of Intercalated Duct Cells and Endothelial Cells in the Isoproterenol-treated Rat Parotid Gland

“…Since then, numerous studies have characterized the morphological alterations of the salivary glands resulting from chronic IPR treatment (Schneyer, 1962;Seifert, 1962Seifert, , 1967Cataldo et al, 1965;Pohto, 1966;Radley, 1969;Menaker et al, 1974;Simson et al, 1974Simson et al, , 1978Bloom et al, 1979;Tuck and Matthiesen, 1980). In general, these studies have focused on the acinar secretory cells: IPR induces a high rate of mitosis in these cells, and they undergo marked structural alterations.…”

Immunohistochemical Analysis of DNA Synthesis During Chronic Stimulation with Isoproterenol in Mouse Submandibular Gland

“…Morphological and biochemical studies on the effects of chronic IPR treatment revealed several changes in the acinar cells of the SMG: an increase in size and alteration of the structure of secretory granules (Takahama and Barka 1967;Radley 1969;Simson et al 1978); enhanced synthesis of DNA, RNA and proteins (Barka 1965a;Radley 1968;Sheetz and Menaker 1979); and induction of the expression of genes encoding secretory proteins (Ann and Carlson 1985;Barka et al 1986a) and of a protooncogene (Barka et al 1986b). These effects of IPR are mediated by ␤ -adrenergic receptors, followed by an increase in cAMP, which acts as an intracellular messenger in the activation of several enzymes associated with exocytosis, synthesis of secretory proteins, cell proliferation (Brenner and Wulf 1989), and other phenomena (Baum 1987;Hand 1990).…”