In vivo exchange of cholesteryl esters from low density lipoproteins to high density lipoproteins.

Labelled cholesteryl esters were injected within low density lipoproteins (LDL) in four subjects. In all experiments, cholesteryl esters transferred to HDL initially, at the rate of about 3% per hour. Very low density lipoprotein cholesteryl esters became labelled later, possibly by transfer from HDL. The simultaneous labelling of HDL free cholesterol by a second isotope (injected within mevalonic acid) showed that the rapid labelling of HDL cholesteryl esters from LDL was substantially faster than that from the esterification of HDL free cholesterol. While this process does not show net transfer of cholesteryl esters from LDL to HDL it indicates a pathway for equilibration of cholesteryl esters among plasma lipoproteins.