Sequence of changes in rat buccal mucosa induced by zinc deficiency

In weanling rats, after receiving a zinc-deficient diet (less than 1 ppm) for 4 wk, the buccal mucosa appears hyperplastic. This study determines changes at earlier stages of the lesion. After 9 days of deficiency, the keratin layer had partially converted to parakeratosis and thickened, and the size of the capillary bed was increased. After 18 days, the keratin layer was fully parakeratotic and thickened further. The cellular layer was thickened. The mitotic rate was doubled and rete ridges were convoluted. After 27 days, the keratin and cellular layers were further thickened, and the mitotic rate remained elevated. The rete ridges were further convoluted. The number of mast cells was doubled and the size of the vascular bed had increased further. These findings suggest early and late interactions between the epithelium and lamina propria. After four days on a control diet following 27 days of zinc deficiency, the mucosa returned normal.