The effect of vitamin A on the proliferation of oral epithelium in the rat.
This study assessed the effect of topical and systemic 13-cis-retinoic acid on rat palatal epithelial proliferation with bromodeoxyuridine labelling and silver stained nucleolar organizer regions. Sixty male Wistar rats were assigned randomly to a control group or treatment groups of topical orabase, RA in orabase, 5 times/week or twice weekly systemic doses of 12 mg RA in coconut oil. The rats were treated for 1, 2, 4 or 8 weeks and killed 1 h post-injection of 40 mg/kg BrdUrd. The palatal mucosae were processed, using immunoperoxidase staining or silver stain to visualize BrdUrd utilization or AgNORs, respectively. The number of BrdUrd positive nuclei/mm overlying epithelium and number and area of AgNORs in the basal cells were assessed using image analysis. ANOVA indicated there was no significant effect of treatment on LN/mm or the numbers or areas of AgNORs. The LN/mm for the 8 w group (29.5) was significantly lower than the other groups. RA did not influence rat palatal epithelial proliferation, but across all groups increased age was associated with decreased proliferation. It would appear that the proliferation of normal oral mucosa may not be subject to altered proliferation when treated with therapeutic doses of topical or systemic RA.