The effect of ultra-violet radiation and restricted diet on rat labial mucosa

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Abstract
The combined effect of UV radiation and a restricted diet on oral mucosa was investigated using the labial mucosa of pigmented rats. Rats (24) were divided so that 12 experimental animals received 50% of the average daily diet of the remaining 12 normal controls. After 1 mo., the epithelium of the restricted group had thinned to 2/3 of that of controls. Nine rats from each group were then subjected to daily UV irradiation of the labial mucosa, 3 animals in each group remaining as unirradiated controls. After 1, 4 and 8 wk irradiation, 3 experimental and 1 unirradiated control from each group were sacrificed. Microscopic examination showed that thickness of the epithelium and the mitotic index increased in normal and restricted animals at 4 wk. Increase in thickness was maintained at 8 wk, but mitotic index declined in deficient animals at this time. Evidence of epithelial dysplasia was seen in normal animals at 4 wk, and this increased at 8 wk; such changes were rarely seen in restricted animals. The extent of UV induced dysplasia may be related to the mitotic index, a lower mitotic index implying less dysplasia.