The erythrocyte membrane structure in patients with mixed hyperlipidemia

: In hypercholesterolemia the damage to the plasma membranes of erythrocytes is observed. This may result from higher concentration of cholesterol in plasma and membranes, lipids peroxidation and changes in protein conformation. The aim of the study was to estimate the membrane fluidity, concentration of cholesterol (Ch), phospholipids (PL), ratio of Ch/PL, thiobarbituric acid reaction substances (TBARS) in the isolated erythrocyte membrane of patients with mixed hyperlipidemia. The study comprised 50 patients in the age from 45 to 65 with the initial concentrations of total cholesterol (TC) > 200 mg/dl (5.2 mmol/l); cholesterol LDL (LDL-C) > 160 mg/dL (4.1 mmol/l); triglicerides (TG) > 150 mg/dL (4.5 mmol/L) and 22 healthy controls. The plasma lipids concentrations were determined by enzymatic method, the concentration of cholesterol membrane (by method of Ilcy), phospholipids (by method of Bartlett), lipids peroxidation (by method of Stocks and Dormandy) and the erythrocyte membrane fluidity (by a spin-label paramagnetic resonance method using 5-doxylstearic acid - 5-DSA, and 16-doxylstearic acid - 16-DSA). The order parameter S was determined using 5-DSA; 16-DSA was used to estimate the correlation taub and tauc. In group of patients with mixed hyperlipidemia in comparison to the control group it was noticed a significant increase of the mean values of order parameter S (0.74 +/- 0.01 vs. 0.72 +/- 0.005, p < 0.001), of membrane cholesterol concentration (3.39 +/-0.98 vs. 1.93 +/- 0.93 mmol/l pc, p < 0.001), ratio Ch/PL (2.32 +/- 1.22 vs. 1.22 +/- 0.44; p < 0,001) and TBARS (2.91 +/- 0.74 vs. 1.5 +/- 0.4 nmol/mg protein). The differences of the correlation times and phospholipids concentrations between the groups were not statistically significant. Significant correlation between the order parameter S and concentrations of TC, LDL-C in plasma and membrane cholesterol was observed. On the base of given results we conclude that mixed hyperlipidemia may have influence on the erythrocyte membrane structure caused significant decrease of membrane fluidity in the superficial layer without any significant changes in deeper layer and significant increase of membrane cholesterol and TBARS.