MORPHOLOGICAL EFFECTS OF DIABETES ON THE GRANULAR DUCTS AND ACINI OF THE RAT SUBMANDIBULAR-GLAND

Effects of experimental diabetes on rat submandibular glands have been documented, but earlier reports suggested that diabetes caused an ext ensive cellular degeneration and a replacement of the parenchymal cell s by fibrous connective tissue. Such observations, however, are diffic ult to reconcile with the relatively normal physiological responsivene ss of the gland (Anderson and Suleiman, 1989). This study, therefore, reexamined the histological, histochemical and ultrastructural effects of streptozotocin-induced diabetes on rat submandibular glands. The t issues were examined at 3 weeks, and 3 and 6 months after the inductio n of diabetes, and compared with glands from age-matched controls by b oth light and electron microscopy. Light microscopi cally, the proport ional volumes of the acini and granular ducts remained constant in con trol rats at about 48% and 38% respectively. In diabetic animals the v olume density of the acini increased progressively to 62%, whereas tha t of the granular ducts decreased to 20%. The diameter and number of g ranular ducts were reduced in diabetic animals, but acinar cell profil e area was only affected 6 months after the induction of diabetes. Ult rastructurally, there was an accumulation of lipid in the acinar cells and, with increasing duration of diabetes, the number of autophagic s tructures in both the acini and the granular ducts increased. Although there was evidence of some cellular degeneration it was never excessi ve. Morphometry showed that the volume density of secretory granules w ithin the acinar cells was unaffected, but there was a significant red uction in the volume density of secretory granules within the granular ducts. Thus, in the rat submandibular gland the greatest effect of st reptozotocin-induced diabetes was to cause hypotrophic changes in the cells of the granular ducts. The relative contributions of a direct ef fect of insulin insufficiency and the hypogonadal effects of diabetes, however, are not known. (C) 1994 Wiley-Liss, Inc.