ERYTHROCYTE-MEMBRANE ALTERATIONS AS A CONSEQUENCE OF LEUKOCYTE ACTIVATION

White blood cells, especially polymorphonuclear neutrophils (PMN), are known to alter some hemorheological parameters. Most of in vitro results have been obtained with passive PMN. Stimulated PMN also lead to other hemorheological changes. In our study, we have firstly activated PMN with opsonized zymosan and collected a PMN-free supernatant after 30 minuts activation. This supernatant was secondarily incubated with erythrocytes either in whole blood or in suspension. After 10 minuts incubation, hemorheological parameters were evaluated: 1) red blood deformability (RBC) (Ektacytometer* Technicon), 2) RBC filtration (Hemorheometer MK 1), 3) RBC aggregation (Erythroaggregometer* Sefam), 4) Plasmatic and whole blood viscosities (Low Shear 30* Contraves). Our results show that activated PMN-supernatant increases rigidity index (IR) of RBC in suspensions (IR of RBC control = 14,59 +/- 3,30 towards RI of incubated RBC = 22,91 +/- 7,06 p < 0,001). Other rheological parameters remain unchanged. Activated PMN suspenatant influence on RBC is slight but could suggest of an alteration of RBC membrane. With an in vitro model of washed platelets aggregation, we have previously demonstrated that proaggregant activity of PMN supernatant was inhibited by specific Platelet-Activating Factor (PAF-acether) antagonists: BN 52021, BN 50723, Web 2086. We have so compared both effects of activated PMN-supernatant and synthetic PAF-acether on RBC membrane fluidity. Membrane fluidity was studied by fluorescence polarization of 4 probes embedded at different deeps in the membrane of intact RBC. Similar modifications of RBC membrane fluidity are observed with either synthetic PAF-acether or PMN supernatant. This effect is significant with the highest concentrations of both PAF-acether and PMN supernatant and appears in the membrane deep labelled with the fluorescent probe 9-(9 anthroyloxy) stearic acid. RBC membrane alterations induced by PMN activation are slight but could have dramatic consequences in microcirculation.