Effects of zinc deficiency on the distribution of membrane-coating granules in rat buccal epithelium.

Nutritional zinc deficiency causes consistent excessive cell proliferation in the epithelium of the buccal mucosa. The number per cell and the intracellular location of membrane-coating granules in this epithelium were investigated in male rats placed at weanling age for a 4-week period on a diet containing 1.2 ppm of Zn and in their pair fed controls. Membrane-coating granules were identified on electron micrographs following their demonstration in thin sections by the use of an alkaline bismuth technique. Counts of membrane-coating granules in the first 4 rows of spinous cells and the last 4 rows of granular cells showed that in the zinc-deficient group (1) the total number of granules per cell was increased; (2) the proportion of granules displaced to the cell periphery was decreased in favor of a higher proportion persisting in the center and (3) there was a marked reduction in number and proportion of granules positioned near the superficial cell membrane. The greater uniformity in the distribution of the granules in the hyperplastic-hypertrophic epithelium of the zinc deficient group suggests weakening of the surface-oriented polarity characteristic of the control tissue.