Effects of two cholesterol derivatives on erythrocytes deformability and membrane fluidity on intact red blood cells and ghosts

Abstract

The purpose of this investigation was to correlate, on intact red blood cells (RBC) , deformability and membrane fluidity. RBC deformability was measured by their filterability through a 4.8 um diameter pore filter and membrane fluidity was tested with trimethylammonium-diphenylhexatriene (TMA-DPR), a specific plasma membrane fluorescent probe. RBC were untreated or experimentaly modified according to Shinitzky's method with 25-OH-cholesterol (25OH-chol) and with cholesterol-hemisuccinate (CHS). These cholesterol analogs are known as rigidifying agents of the membranes. Whereas 25OH-chol treatment did not induce any change of fluidity and filterability on intact RBC, CHS treatment provoked most modifications on intact RBC: it induced a membrane fluidization (as compared to control cells) and a spherocytosis with a 5.5% increase of the mean corpuscular volume (MCV), without any alteration of filterability measurements. Concurrently fluorescence polarization measurements on ghosts obtained from CHS treated cells, which retain hemoglobin, did not show significative fluidity modification whereas 25OH-chol treatment decreased it. We conclude that there is no direct correlation between erythrocyte deformability as measured by filterability and membrane fluidity on entire cells. It appears to be of a great importance to test fluidity on ghosts and on intact cells. Different membrane localisation of the two cholesterol derivatives tested may explain their different impact on membrane.