IN-VIVO SHEAR-FLOW AND ERYTHROCYTE-MEMBRANE FLUIDITY IN HYPERTENSIVE PATIENTS

1 To evaluate the response of red blood cells subjected to the shear f low in hypertension, the relationships between wall shear phenomena de termined in vivo in the brachial artery of hypertensive patients and t he. modifications of the membrane dynamics measured in vitro in erythr ocyte ghosts of 32 patients were investigated. 2 Two fluorescent probe s, diphenylhexatriene (DPH) and its trimethylamino-derivative (TMA-DPH ), localized respectively in the lipid membrane core and at the lipid- water interface, were used. 3 Shear rate, shear stress and blood veloc ity were positively correlated with TMA-DPH anisotropy (P = 0.015, 0.0 05 and 0.026, respectively), but not with that of DPH. This indicates that wall shear forces were associated with the microviscosity of the outer part of the cell membrane. 4 The changes in wall shear forces an d erythrocyte membrane microviscosity probed by TMA-DPH or DPH were ob served to vary in parallel under nitrendipine therapy. 5 These results suggest that in vivo shear forces participate in the control of eryth rocyte membrane fluidity or that erythrocytes adapt their membrane pro perties to blood flow conditions.