TRANSBILAYER MOVEMENT OF ERYTHROCYTE-MEMBRANE CHOLESTEROL IN HUMAN ESSENTIAL-HYPERTENSION

Objective: To study whether the rate of transbilayer movement of membr ane cholesterol is impaired in erythrocyte membrane of normo- and hype rcholesterolaemic patients with untreated essential hypertension. Desi gn: An observational case-control study. Methods: Erythrocytes were pr epared from venous blood samples obtained from normotensive subjects a nd hypertensive patients. The rate of transbilayer movement of membran e cholesterol was monitored in intact erythrocytes, using a radiolabel led cholesterol tracer. Erythrocytes were treated briefly or continuou sly with cholesterol oxidase to convert a portion of the outer leaflet cholesterol to cholestenone, and the specific radioactivity of choles tenone was determined over the period of tracer equilibration. The dec rease in specific radioactivity of cholestenone reflected the transbil ayer movement of radiolabelled cholesterol. Results: There were no sig nificant differences between the diffusion of cholesterol across the e rythrocyte membrane of normo- and hypercholesterolaemic hypertensive p atients, 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 patient s, after a brief and after a continuous cholesterol oxidase treatment, respectively. Conclusion: There is a reduction in the transbilayer mo vement of membrane cholesterol in erythrocytes of patients with untrea ted essential hypertension.