Alterations in the lipid content of rat palatal epithelium during carcinogenesis

The hard palates of 150 female albino rats of the Sprague-Dawley strain were painted 3 times a week either with the fat-soluble carcinogen 7,12-dimethylbenz(a)anthracene (DMBA) for 11 months with inhibited secretion of saliva or with the water-soluble carcinogen 4-nitrochinoline N-oxide (4NQO) for 8 months with intact salivary secretion. Specimens were taken regularly from the mucosa of the hard palate, and the content of lipids in the epithelium was studied histochemically and biochemically during the carcinogenesis. Changes in the lipid content could be observed histochemically as there was a focal loss of lipid stainability in the epithelium during the more advanced stages of carcinogenesis with severe epithelial dysplasia, carcinoma in situ and early invasive carcinoma. The biochemical method used (TLC) could not, however, verify the histologically observed changes in the lipid content of the epithelium, probably because the changes were very local.