Histochemical localization at the electron microscopic level of sulfated glycosaminoglycans in the rat gingiva

Using the high iron diamine thiocarbohydrazide silver proteinate (HID-TCH-SP) staining technique, we investigated ultrastructural localization of sulfated glycosaminoglycans (GAGs) in the rat gingiva shortly after eruption, especially those associated with internal and external basal laminae. In the apical portion of the internal basal lamina, HID-TCH-SP stain deposits were distributed mainly in the region of the lamina lucida located between the lamina densa and the distal surface membrane of the junctional epithelium and inside the depression of the distal surface membrane adjacent to the basal lamina. Stain deposits were also detected on the surface membrane of the cytoplasmic protrusion. Interestingly, the density of HID-TCH-SP stain deposits in the internal basal lamina was highest in the apical portion of the junctional epithelium and decreased in the coronal direction, finally tending to disappear completely. On the other hand, in the external basal lamina the deposits were localized in the whole region of the basal lamina or at both sites of the lamina densa. HID-TCH-SP stain deposits were also detected external to the lamina densa in the basement membrane associated with capillaries and in the connective tissue where they were distributed in close relation to collagen fibrils. Testicular hyaluronidase digested most HID-TCH-SP stain deposits in the connective tissue, whereas those in the region of basement membranes resisted this enzymatic digestion.