Damage to the structure of erythrocyte plasma membranes in patients with type-2 hypercholesterolemia

Background: Hypercholesterolemia may decrease the deformability of red blood cells which impairs their hemorheological behavior and promotes atherosclerosis. The study involved 60 hypercholesterolemic patients and 30 healthy individuals as the control group. Methods: The membrane fluidity of erythrocytes was estimated by a spin-label method (5-doxylstearic acid (5-DSA)). The ratio of weakly to strongly (W/S) immobilized residues of erythrocyte membrane-bond maleimide-tempo spin label was studied in oxidative damage to membrane protein. Damage to erythrocyte proteins was also indicated by means of Na+ K+ ATPase activity. Results: The membranes of hyperlipidernia (hlp) patients contain larger concentrations of cholesterol 2.16 +/- 0.24 than do those of the normolipemic individuals 0.31 +/- 0.24 (P < 0.001). The level of Na+ K+ ATPase in the erythrocyte membrane from the control group was higher 103.4 +/- 1.3 (nmol Pi/(mg proteins h)) than in the patient group 93.6 +/- 3.2 (nmol Pi/(mg proteins h)) (P < 0.001). The order parameter S 5-DSA in the control group was 0.745 +/- 0.009 and in hlp patients was 0.755 +/- 0.009 (P < 0.001). The W/S ratio in the control group amounted to 2.00 +/- 0.09 and in the hlp patient group was 2.50 +/- 0.11 (P < 0.001). Conclusion: Type-2 hypercholesterolemia causes changes in the structure and fluidity of erythrocyte plasma membranes since the excess of cholesterol affects the normal rheology of blood through its interaction with erythrocytes. It also impairs the function and structure of plasma membrane proteins. (C) 2003 Elsevier Ltd. All rights reserved.