Measurement temperature plays a pivotal role in the distribution of erythrocyte deformability after LPS

Reductions in red blood cell membrane deformability (RBC(D)) may perturb microcirculatory blood flow and impair tissue O(2)-availability. We investigated the effect of assay temperature on the distribution of RBC(D) in endotoxin (LPS) incubated and control RBCs. Fresh blood from healthy rats was incubated with and without the presence of LPS for 6 hrs. An index of red blood cell membrane deformability, delta, was measured via the micropipette aspiration technique at 25 degrees C and 37 degrees C at 0, 2 and 6 hrs of incubation. The ATP content of RBC was measured by the luciferin-luciferase technique. At 25 degrees C, LPS caused a significant decrease in mean delta after 2 and 6 hours incubation compared to controls (-10.0%, p=0.03 and -24.0%, p=0.03, respectively) characterized by a left shift in the distribution (skewness: -1.4). However, at 37 degrees C a significant decrease in delta was only detected after 6 hrs of LPS incubation (-13.8%, p=0.01, compared to -5.1%, p=0.7 at 2 hours) and lacked the left shifted distribution (skewness: 0.2). No significant difference in ATP content of RBCs was observed between groups. We have shown that LPS incubation results in a significant decrease in RBC(D) and that room temperature measurement of physical membrane properties may exaggerate the differences between normal and perturbed RBCs.