ObjectiveTo determine whether the cholesterol distribution is impaired in erythrocyte membranes of normo- and hypercholesterolaemic patients with untreated essential hypertension.DesignObservational case-control study.MethodsErythrocytes were prepared from venous blood samples obtained from normotensive subjects and hypertensive patients. The membrane cholesterol distribution was measured by cholesterol oxidation to cholestenone after continuous cholesterol oxidase treatment. The membrane cholesterol content was determined. The ability of cells to be labelled with [3H]-cholesterol was also tested.ResultsThe cholesterol distribution was asymmetric in erythrocyte membranes of the control subjects and hypertensive patients. The oxidation rate was faster in normotensive subjects, and no differences were found between normo- and hypercholesterolaemic hypertensive patients. Total cholesterol mass was lower in erythrocyte membranes of hypertensive patients, as indicated by a higher incorporation of radioactive cholesterol.ConclusionThese data suggest that the membrane cholesterol distribution is impaired in patients with untreated essential hypertension, and support the presence of cholesterol-rich domains in the erythrocyte membrane inner monolayer.