Lipid composition and physical properties of membranes from C-6 glial cells with altered phospholipid polar headgroups.

Growth of C-6 glial cells in media enriched in the polar headgroup precursors N,N-dimethylethanolamine, N-monomethylethanolamine or ethanolamine for 24 h resulted in the accumulation of the corresponding phospholipids to about 30% of total membrane phospholipid. Under these conditions the cholesterol to phospholipid ratios were unaffected. With the exception of arachidonic acid, which was significantly reduced in the lipids from cells grown in the presence of N-monomethylethanolamine, the fatty acid composition of cells grown under the various conditions was identical. The physical properties of membranes prepared from these cells were compared by electron spin resonance spectroscopy using spin-labelled stearic acid. Modifications in cellular phospholipid composition did not affect either the order parameter or the correlation time of fatty acid spin labels. Since there are no significant effects on the other membrane lipids and since the physical properties of the membranes are maintained, these modifications in phospholipid composition provide a valuable means for studying the role of phospholipid polar headgroups in the function of membrane-bound enzymes and hormone receptors in C-6 cells.