ROLE OF THE LEUKOCYTE IN ENDOTOXIN-INDUCED ALTERATIONS OF THE RED-CELL MEMBRANE

Sepsis and endotoxemia are known to be associated with alterations in the red cell membrane that result in diminished flexibility. This decr eased flexibility may be responsible, in part, for the microcirculator y abnormalities accompanying sepsis. The etiology of these sepsis-asso ciated changes remains unclear. This study evaluates the role of the w hite blood cell in these abnormalities. Specimens were obtained from 4 4 volunteers and divided into two treatment groups. Group I specimens were incubated with Escherichia coli endotoxin (2 mug/ml) followed by removal of the white blood cells. The white blood cells were removed f rom group II specimens before endotoxin incubation. Paired, saline-inc ubated samples served as controls. After incubation, washed erythrocyt es were evaluated for deformability and membrane viscosity. Deformabil ity was assessed by filtration through 4.7-mum membranes. Red cell def ormability was expressed as filtration rate (volume of cells per secon d per square centimeter). Membrane viscosity was assessed by fluoresce nt spectroscopy of cells into which the membrane probe (trimethylamino )-phenyl)-6-phenyl-1,3,5-hexatriene had been incorporated. Results wer e expressed as anisotropy. Endotoxin resulted in a significant increas e in erythrocyte membrane viscosity (experimental, 0.296 +/- 0.002 vs. control, 0.284 +/- 0.002, P < 0.001). This was reflected by a signifi cant decrease in cellular deformability (experimental, 142.55 +/- 6.55 vs. control, 157.86 +/- 8.63, P < 0.01). However, these alterations a re not a direct effect of endotoxin, but require the presence and part icipation of the white blood cell and/or its mediators (experimental, 0.301 +/- 0.002 vs. control, 0.300 +/- 0.001, P = NS).