[Study on the mechanism of denuded tongue coating due to yin deficiency]

Denuded tongue coating is an important sign of serious Yin deficiency. The total number of exfoliated cells increased in the imprint of a Yin-deficient tongue. Not only the cells of the superficial layer but those of the middle layer appeared. Many necrotic cells could also be seen. This picture showed that the cell exfoliation rate of a Yin-deficient tongue was faster than in a normal tongue, caused chiefly by the degeneration and necrosis of the epithelial cells. It is believed that cell necrosis is the principal feature of the Yin-deficient tongue. This is in accordance with the TCM theory that denuded tongue coating is due to exhaustion of Yin fluid. Study on lingual morphology: The filiform papillae disappeared in slices of Yin-deficient tongue. The fungiform papillae had atrophied, the number of strata of epithelial cells reduced, and there were no complete keratinocytes or granules, tonofilaments and membrane coating granules in the cytoplasm. Observation of the microcirculation of fungiform papillae of a Yin-deficient tongue showed: the structure of vessels was abnormal, blood flowed slowly, red blood cells aggregated and the vessels dilated. Microcirculation of the blood was stagnant. The disturbance of microcirculation could accelerate the abnormal metabolism of lingual epithelial cells and cell necrosis, resulting in denuded tongue coating. Analysis of salivary zinc level: The salivary zinc level (0.232 micrograms/ml) of the patients with Yin-deficient tongue was significantly higher than that of healthy subjects (0.099 micrograms/ml). Zinc can affect the formation and function of nuclear spindle in cellular mitosis. The change of zinc level may be a pathogenic factor in Yin-deficient tongue.