Validation of an in vitro method for incorporating labelled cholesterol into human erythrocytes

At least 85% of the cholesterol of human erythrocytes can be replaced by isotopically labelled cholesterol, by incubation of the cells with the plasma lipoprotein HDL3 into which labelled cholesterol has been incorporated from Celite. With erythrocytes containing 40% labelled cholesterol, the reactivity of the incorporated labelled cholesterol was the same as that of the remaining native cholesterol with regard to: oxidation by cholesterol oxidase for both intact erythrocytes and cell ghosts, extraction by cholesterol depleted plasma, and exchange for HDL3 cholesterol. Also, the reactivity of the cholesterol in the cells in which labelled cholesterol was incorporated was the same as in untreated erythrocytes.