Transfer of excess cholesterol from human red blood cells to plasma in vitro.

This study examined the ability of plasma and plasma fractions from normolipidaemic subjects and plasma from a patient with homozygous familial high density lipoprotein deficiency (Tangier disease) to promote loss of excess cholesterol from red blood cells in vitro. Isolated high density lipoproteins were the most potent plasma fraction for removing excess cellular cholesterol. Lipoprotein-deficient plasma and human serum albumin, but not very low density lipoproteins and low density lipoproteins, also removed excess cholesterol from the red blood cells. The near absence of high density lipoproteins in plasma from the patient with Tangier disease did not result in an abnormally low rate of cholesterol loss from the enriched red blood cells. These results suggest that normal levels of high density lipoproteins are not vital for the removal of excess cholesterol from red blood cells by plasma.