Oral epithelial cell lipid synthesis in the presence of retinoic acid or nitrosonornicotine.

The current study examines the effects of N-nitrosonornicotine (NNN) and all trans-retinoic acid (RA) on the synthesis and composition of lipids of oral epithelial cells grown in culture. Cells were exposed to NNN, RA or methylene chloride (the vehicle for the NNN and RA) and the lipids labelled with [14C]-acetate. Lipids were extracted from the cells, separated by paper chromatography, located by autoradiography, and acetate incorporation determined by liquid scintillation spectrometry. Cholesterol labelling was significantly decreased by the RA between 4 and 48 h when compared to the NNN-treated or control cells. After 48 h the incorporation levels in the presence of the two last compounds decreased. Free fatty acid labelling was also significantly less in cells exposed to RA, while labelling of triglycerides and phospholipids was increased. N-nitrosonornicotine seemed to produce a decreased labelling of cholesterol after 96 h continuous exposure. The results of these studies suggest that retinoid rapidly elevates the cell content of lipid formed from the glycerolipid pathway and membrane mechanisms may be modulated by this effect.