Effects on cell adhesion and membrane fluidity of changes in plasmalemmal lipids in mouse L929 cells.

It has recently been shown that the lipid composition of the plasmalemma may be altered by taking advantage of the acyltransferase system to incorporate selected fatty acids into phosphatidyl lipids of the plasmalemma. Such lipid alterations have been shown to effect changes in cell adhesion in chick neural retina cells. Based on the fluid-mosaic model, it has been suggested that such changee in cell behaviour may be related to the degree of plasmalemmal fluidity. In the present study, when mouse L929 cells are incubated in the presence of stearic or arachidic acid (saturated), cell adhesion levels, as measured by an assay based on cellsubstrate interaction, increase. Similar incubation with linoleic or linolenic acid (unsaturated) decreases cell adhesion. In addition, we have found significant changes in plasmalemmal fluidity, using an assay based on patching of fluorescent antibody. Unsaturated fatty acids have a fluidizing effect on the membrane, while saturated fatty acids exert a solidifying effect, when substituted into the membrane. Although alternative interpretations are possible, we suggest that membrane fluidity changes are induced by alterations in lipid thermal transition temperatures of plasmalemmal phosphatidyl compounds, in which fatty acid substitutions were made. We also suggest that changes in membrane fluidity might affect adhesion by altering the aggregability of any membrane sites that may be involved in adhesion. Although a very fluid membrane may allow rapid lateral migration of sites, it might also aid their rapid dispersal, thereby reducing adhesion.