Morphologic changes in the granular convoluted tubule cells of the mouse submandibular gland following hypophysectomy and hormonal replacement

Abstract

 Morphological changes in the granular convoluted tubule (GCT) cells of the male mouse submandibular gland (SMG) were examined following hypophysectomy and hormonal replacement. Semithin sections stained with Heidenhain's iron hematoxylin showed that hypophysectomy severely regressed the GCT phenotype. Although only a few dispersed cells containing secretory granules were observed in the GCT segments under a light microscope, electron microscopy revealed that many regressed cells continued to constitutively elaborate apical secretory granules (although they were very small) and contained a euchromatic nucleus at the center of the cell, poor rough endoplasmic reticulum (RER) and Golgi apparatus in the perinuclear region, and well-developed basal infoldings. These findings suggest that hypophysectomy resulted in atrophy of GCT cells, but that they retained evidence of being secretory cells. 5α-Dihydrotestosterone (DHT); 3,5,3′-triiodo-l-thyronine (T₃); and dexamethasone (Dex) each enhanced the GCT phenotype of hypophysectomized males to some degree. Combined hormonal replacement with DHT + T₃ in hypophysectomized males restored a nearly normal male GCT phenotype with a full complement of secretory granules and rare basal infoldings, whereas T₃ alone induced a normal female-like GCT phenotype, with considerably abundant secretory granules and the usual short basal infoldings, in hypophysectomized male glands. Furthermore, Dex was found to synergistically enlarge secretory granules when administered with T₃ and/or DHT, although it was only weakly effective in enhancing the GCT phenotype when used alone. Taken together, the above findings confirmed that the GCT phenotype of the mouse SMG is regulated by the synergistic action of pituitary-dependent hormones.