Regional differences in gradients of dry residue density in oral epithelia of the rat: a quantitative study

Elemental and cytochemical localization of calcium in rat cheek epithelium

Energy-dispersive X-ray microanalysis, combined with scanning electron microscopy, was applied to 18 microns thick freeze-dried cryosections to determine the level of calcium in successive layers of the epithelium. This indicated low levels of calcium in basal cells, high in spinous cells, moderate in granular cells, lowest in the inner keratin and highest in the outer keratin layers. The potassium pyroantimonate technique was used to study the cytochemical distribution of Ca2+. The reaction product, calcium pyroantimonate (Ca-PA), was generated from cellular and intercellular calcium by perfusion of the anaesthetized rat with a solution of potassium pyroantimonate in glutaraldehyde. Ca-PA was localized in nuclei, mitochondria, lysosomal-type bodies and membrane-coating granules. A denser Ca-PA distribution was found between upper spinous and lower granular cells. The proposed identification of Ca2+ as a major component in Ca-PA was confirmed by EDTA decalcification and X-ray microprobe analysis of the reaction product. Thus X-ray microanalysis in combination with cytochemistry can localize Ca2+ in a growing and differentiating tissue such as stratified squamous epithelium.

Epithelial dimensions and capillary supply in the oral mucosa of the rat

Subdividing the cheek, palate and ventral tongue into seven anatomically identifiable regions enabled us to assess relationships that were previously obscured by the great heterogeneity of rat oral epithelium. Capillaries were visualized by an alkaline phosphatase azo dye method in oral mucosa of four 3-month old male rats. Basal layer length per unit surface length showed a statistically significant relationship with the thickness of the epithelial cell layer in all seven regions. Linear regression of mean regional length of basal layer on mean thickness of the cellular layer in the seven regions was statistically highly significant. This was true also for mean capillary length. Thickness of the cellular layer, length of the basal layer and capillary length were similar in a palatal ruga and a thick region of cheek, suggesting that epithelial thickness rather than the type of mucosa influences the magnitude of these values. Proportional reductions in all three variables were observed in a second region of cheek and a region of ventral tongue, supporting this suggestion.