Influence of fatty acid composition in mammalian erythrocytes on cellular aggregation

The rheologic properties of red blood cells (RBC) are determined by humoral and cellular factors. Fatty acid compo- sition of the RBC phospholipid bilayer is one factor influencing membrane fluidity this could affect RBC aggregation because of a higher bias of RBC deformability. The present investigation was performed to investigate a possible relationship between fatty acid composition and erythrocyte aggregation using animals with high RBC aggregation (horse and pig) and animals with immeasurable RBC aggregation (sheep). Horse and pig showed similar distribution of the four major components palmitoleic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1n9), and linoleic acid (C18:2n6). The sheep's saturated fatty acids C16:0 and C18:0 were decreased, whereas unsaturated oleic acid (C18:1n9) showed a two fold increase in comparison to horse and pig. It can be assumed that the fatty acid bilayer is a minor factor influencing erythrocyte flexibility due to its influence on membrane fluidity and therefore there might be an existing link to erythrocyte aggregation. The sheep has relatively dense erythrocytes with low cell volumes. Therefore, the absence of aggregation might be postulated to arise from geometric factors against the expected effect of unsaturated fatty acids on membrane fluidity, the higher level of unsaturated fatty acids in ovine erythrocytes over that found in horse and pig was surprising. The present result, which accords with former studies, indicates that the geometric factor given by the intracellular skeleton overrides any effect of membrane composition on aggregation in sheep.