Distribution and transbilayer movement of membrane cholesterol in erythrocyte of patients with essential hypertension

Abstract

The participants were 12 healthy subjects, 12 normocholesterolaemic hypertensive and 12 hypercholesterolaemic hypertensive patients. Venous blood samples were collected in Trabajo ganador del VIII Premio Sociedad Andaluza de Medicina Interna. «Dr. López Laguna» 0.38% sodium citrate. Erythrocyte membrane cholesterol distribution and transbilayer movement were measured according to the continuous cholesterol oxidase treatment. Erythrocyte Na⁺-Li⁺ countertransport activity was determined by measurements of Li⁺ efflux in the presence or absence of Na⁺.The statistical analysis was conducted for significance by using ANOVA for paired data and correlations were carried out by linear regression analysis using Pearson's correlation coefficient. Our findings are consistent with the presence of cholesterol-rich domains randomly distributed in the human erythrocyte. Cholesterol appeared to be similarly enriched in the cytofacial monolayer but the size of such structural cholesterol pool was greater in erythrocytes of hypertensive patients than in those of healthy subjects. There was also a decrease in the movement rate of erythrocyte membrane cholesterol, which contributed to keep impaired the asymmetric distribution of cholesterol in hypertensive patients. In addition, there was a strong correlation between the half-time for membrane cholesterol distribution or transbilayer movement and erythrocyte Na⁺-Li⁺ countertransport activity, a well known marker of inherited predisposition to essential hypertension. Our data indicate that the steady-state distribution of membrane cholesterol and cell cholesterol exchange may be intimately linked to the etiology of essential hypertension, and to other diseases which are associated to alterations in the lipid metabolism.