Age-related changes in the epithelial dimensions and capillaries of the oral mucosa of the rat.

Seven homologous regions of the oral mucosa were compared in rats 6, 18 and 30 months of age. Capillaries were visualized by their alkaline-phosphatase activity revealed by an azo-dye. Measurements on tracings of densely-spaced histological sections in two planes perpendicular to the epithelial surface showed epithelial thickness in masticatory mucosa decreased by 18 months, but increased by 30 months. In regions of lining mucosa, thickness increased by 18 months, but decreased by up to 13 per cent at 30 months. The size of the capillary bed increased substantially by 18 months and further increased by 30 months. Variability in the epithelial dimensions increased up to 18 months but not beyond; variability in the capillary measurements showed no change with age. The quantitative relationship between epithelial thickness and the size of the epithelial-connective tissue interface and the capillary bed remained unchanged with age.