Effect of lipid A on the deformability, membrane rigidity and geometry of human adult red blood cells

. Lipid A is responsible for the activities of endotoxin and may cause circulatory failure and haemolysis. This study evaluated the effects of different lipid A concentrations on red blood cell (RBC) deformation (rheoscope), the aspiration pressure required to aspirate RBC into 3.3 μm pipettes, the membrane shear elastic modulus (i.e. membrane rigidity) and cellular geometry (micropipette system) after 15 min of incubation. Lipid A concentrations of 10 and 100 μg ml-1 of RBCs decreased RBC deformability by 26% and 39%, respectively. The aspiration pressure for RBCs into a 3.3 μm micropipette increased by 235% at a lipid A concentration of 10 μg ml-1 and by 586% at a concentration of 100 μg ml-1. The elastic shear modulus almost doubled at a lipid A concentration of 10 μg ml-1 and tripled at 100 μg ml-1. At a lipid A concentration of 100 μg ml-1, 37% of RBCs showed spicules. These echinocytes were less deformable than discocytes. Mean corpuscular volume, RBC volume and surface area were not affected by lipid A. We conclude that lipid A causes marked reduction of RBC deformability due to increasing membrane rigidity.