Objective: To study whether the rate of transbilayer movement of membrane cholesterol is impaired in erythrocyte membrane of normo- and hypercholesterolaemic patients with untreated essential hypertension.
Design: An observational case-control study.
Methods: Erythrocytes were prepared from venous blood samples obtained from normotensive subjects and hypertensive patients. The rate of transbilayer movement of membrane cholesterol was monitored in intact erythrocytes, using a radiolabelled cholesterol tracer. Erythrocytes were treated briefly or continuously with cholesterol oxidase to convert a portion of the outer leaflet cholesterol to cholestenone, and the specific radioactivity of cholestenone was determined over the period of tracer equilibration. The decrease in specific radioactivity of cholestenone reflected the transbilayer movement of radiolabelled cholesterol.
Results: There were no significant differences between the diffusion of cholesterol across the erythrocyte membrane of normo- and hypercholesterolaemic hypertensive patients, but the rates were significantly lower than that estimated in control subjects. The mean +/- SD half-times for the process were 55.1 +/- 8.8 and 11.3 +/- 2.1 min in controls, 63.1 +/- 9.2 and 15.8 +/- 2.3 min in normocholesterolaemic hypertensive patients, and 66.2 +/- 9.4 and 16.2 +/- 1.7 min in hypercholesterolaemic hypertensive patients, after a brief and after a continuous cholesterol oxidase treatment, respectively.
Conclusion: There is a reduction in the transbilayer movement of membrane cholesterol in erythrocytes of patients with untreated essential hypertension.