In vivo metabolism of esterified cholesterol and apoproteins in rabbit plasma low density lipoproteins.

Preparations of rabbit low density lipoproteins (LDL) labelled with 3H in the esterified and free cholesterol moieties and with 125I in the apoprotein moiety were injected intravenously into other rabbits. A substantial proportion of the esterified [3H]cholesterol removed from LDL during the first 30 min was recovered in the high density lipoprotein (HDL) fraction, while no such transfer of labelled apoprotein was observed. There was a clear cut differential in the decay of the different LDL components, slowest for the apoprotein, intermediate for esterified cholesterol and fastest for free cholesterol.