The fate of cholesteryl linoleyl ether and cholesteryl linoleate in the intact rat after injection of biologically labeled human low density lipoprotein.

In vitro labeling of low density lipoproteins (LDL) with [7 alpha(n)-3H]cholesteryl linoleyl ether, and with [4-14C]cholesteryl linoleate was achieved by a modification of the method developed for labeling of very low density lipoproteins. [3H]Cholesteryl linoleyl ether and [14C]cholesteryl linoleate were cosonicated with partially delipidated high density lipoprotein (HDL) and the HDL was purified by centrifugation at d = 1.063. LDL was labeled by incubation of the labeled HDL in the presence of the d greater than 1.25 fraction of human plasma and reisolated at d = 1.063. The 3H/14C ratio in the labeled LDL was the same as in the HDL. The labeled LDL had the same lipid composition and ultrastructural appearance as the non-incubated LDL. After injection into rats, both labels disappeared at similar rates and the t1/2 between 1-24 h was 7.0 h. Up to 8 h after injection of labeled LDL, 94-97% of 3H and 14C radioactivity in the plasma was precipitable by heparin-manganese. 24 h after injection, 28% of the [3H]cholesteryl linoleyl ether was recovered in the liver, 6% in small intestine and 34% in the carcass, and the rest was distributed among all other organs; total recovery of 3H label was 89 +/- 3.0%. The present findings indicate that as in the rat there is no transfer of esterified cholesterol among plasma lipoproteins, LDL is catabolized by both the liver and extrahepatic tissues.