Changes in the lipid composition of a cell membrane due to the binding of one cell modulator may affect binding of a second modulator, whether that binding is receptor-mediated (specific) or non-receptor-mediated (nonspecific). Such altered binding interactions have been demonstrated in oral epithelial cells, wherein N-nitrosonornicotine (NNN), a nonspecific ligand, enhances phorbol ester binding. To characterize membrane changes that may be responsible for such an effect, the current study examined lipid changes in hamster oral epithelial (HCP) cells associated with NNN binding. HCP cultures at two cell densities, 5 × 106 cells/100 mm plate (subconfluent cultures) or 10 × 106 cells/100 mm plate (confluent cultures) were incubated in Keratinocyte-Serum-Free Medium and exposed to 10 µM NNN or DMSO (solvent control) for 48 h. Lipids were labeled with14C-acetate, then extracted, separated by thin layer chromatography, and the14C-lipids located by autoradiography and counted. Exposure of subconfluent cultures to NNN for 48 h, with14C-acetate present during the final 24 h, resulted in altered phospholipid and fatty acid labeling. Phospholipid labeling increased slightly in the presence of NNN compared to controls, while fatty acid labeling showed a modest but significant decrease in the presence of NNN. Similar changes occurred in the confluent cultures. Prelabeling of lipids in subconfluent cultures, followed by exposure to NNN in the absence of radiolabel, resulted in significantly (P<0.05) greater phospholipid labeling in the presence of NNN compared to control cultures. At the same time, fatty acid labeling decreased significantly. The NNN caused the cells to have decreased levels of several long chain polyunsaturated fatty acids and an increased amount of one long chain saturated (24:0) fatty acid. Significant differences were detected in the synthesis of various lipid classes between subconfluent and confluent cultures, but the presence of the NNN did not affect these differences. These results suggest that there is a shift of fatty acid type in the cells’ phospholipids in the presence of NNN, a finding that may reflect the membrane’s adaptation to the modulator’s presence.
|Original language||English (US)|
|Number of pages||5|
|Journal||In Vitro Cellular & Developmental Biology - Animal: Journal of the Society for In Vitro Biology|
|State||Published - Apr 1995|
ASJC Scopus subject areas
- Developmental Biology
- Cell Biology