LOW-DENSITY LIPOPROTEIN-CHOLESTERYL ESTER-DERIVED LINOLEIC-ACID IS MAINLY INCORPORATED INTO THE PHOSPHOLIPID COMPONENT OF THE MACROPHAGES

The cellular metabolism of the cholesterol in the low density lipoprot ein cholesteryl ester (LDL-CE) moiety is well characterized, whereas t he cellular fate of the fatty acid (mainly linoleic acid) in the LDL-C E has not been studied in detail. The distribution of the LDL-CE-deriv ed linoleic acid among cellular lipids was studied in J-774 A.1 macrop hages, using LDL that was radiolabeled in the linoleic acid of its CE moiety. Macrophages were incubated with radiolabeled LDL for 4 h at 4 degrees C, washed and further incubated for up to 24 fi at 37 degrees C in a fresh medium (without LDL). The distribution of the linoleic ac id among cellular lipids was then analyzed. After 20 min of incubation , most of the linoleic acid was found in the CE fraction as a constitu ent of the internalized LDL, and the CE-associated linoleate was progr essively decreased. In parallel, the linoleic acid was found to be est erified into the macrophage phospholipids (mostly in the macrophage ph osphatidyl choline fraction), accounting for up to 62% of the total ce llular labeled linoleic acid after 24 h of incubation. We conclude tha t the fatty acid derived from the hydrolysis of the LDL-CE moiety in m acrophages is mainly incorporated into the cellular phospholipids wher e it can serve for various cellular metabolic processes.