Time-related changes induced by zinc-deficient diet in the concentration of rat cheek epithelial membrane-coating granules

Weanling male Sprague-Dawley rats were fed a diet containing 0.4 parts/ 10⁶ zinc and controls were fed an identical diet supplemented with 40 parts/ 10⁶ zinc. After 9, 18 and 27 days of zinc deficiency, specimens were excised from cheek epithelium and processed for transmission electron microscopy to study the concentration of membrane-coating granules (MCG). Their concentration was increased in the granular-cell layers of the zinc-deficient epithelium and became significantly greater after 18 and 27 days than 9 days of deficiency. MCGs appeared in the parakeratinized layers of zinc-deficient epithelium and their concentration became significantly greater after 27 days in comparison with 9 and 18 days of deficiency. Thus the intracellular retention of MCGs was increased in the granular and parakeratinized layers with the increase in time of zinc deficiency.