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[Study on the deficiency of trace element induced by aging. 2. Effects of zinc deficiency on rats oral mucosa].

Histopathological and ultrastructural changes due to a zinc low diet were investigated in buccal, palatal and tongue mucosa of male 15 weeks rats of Sprague Dawley. Experimental rats were fed with zinc low diet (1.3 ppm Zn) for 16 weeks. After 16 weeks, experimental rats were then kept on zinc-sufficient diet (50 ppm Zn) for 4 weeks during recovery experiment. Results were as follows: 1. Zinc concentrations of serum and submandibular gland were decreased significantly (P less than 0.01) from 2 to 16 weeks respectively. Hair zinc concentrations did not show any significant changes until 4 weeks. But after 8 weeks, those values were lowered significantly (P less than 0.01). Those zinc concentrations were increased gradually after recovery experiment. 2. Hyperparakeratosis were consistent findings in buccal mucosa, ventral surface and interpapillary mucosa of tongue. Keratohyaline granules in those areas diminished in both size and number. Tonofilaments and ribosomes were increased in cells of granular layer, but did not associated with those granules closely. 3. Hyperparakeratosis were rarely seen in palatal mucosa and filiform papilla of tongue in the experimental rats. Marked hyperorthokeratosis was seen in filiform papilla, and eosinophilic granules in cells of granular layer were increased in both size and number. These granules were closely associated with tonofibrils. 4. These pathological changes were restored to normal after recovery experiment at 2 weeks. The present results show that zinc deficiency may impede the process of physiological keratinization of oral mucosa in various degrees. It is suggested that zinc deficiency may have a serious consequence on the oral mucosa in its tolerance.