Parakeratosis of the labial mucosa in zinc-deficient rats.

Epithelial parakeratosis has been observed in zinc-deficient animals of several species. In the rat, it has been reported on the epidermis, footpad, esophagus, soft palate, buccal mucosa, and dorsal tongue. This study reports that the lower lip also shows a striking hyperparakeratosis, as well as epithelial hyperplasia and an increase in mitoses. The appearance of these features was rapid with changes noted at Day 7 and persisting through Day 14 and Day 28. On Day 32, zinc was restored to the diet at control levels and by 42 days the zinc-deficient group showed dramatic increases in food intake, body weight, femur zinc and, in addition, mucosa of the lower lip resembled zinc-adequate controls. These differences are statistically significant. Morphometric comparison of spinous cells from zinc-deficients with those of the controls did not show significant differences.