Abstract
Effects of palmitic acid (PA), linoleic acid (LA), glycerol (G) and L-α-palmitoyl-lysolecithin (LL) on cholesterol esterification in LDL and HDL3 were investigated. Plasma fraction of the density greater than 1.25 was used as LCAT. LDL (1.019<d<1.055) and HDL3 (1.125<d<1.21) was collected by ultracentrifugation. LCAT, LDL and HDL3 were dialyzed exhaustively at 4°C against 0.15M NaCl solution (which contained 5mM EDTA, pH 7.4). Palmitic acid, LA, G and LL were disolved in 3% FFA-poor BSA containing 0.15M NaCl buffer. 3H-FC labeled LDL or HDL3, LCAT and the test substance were incubated at 37°C for two hrs.
Cholesterol esterification rate in LDL was approximately one-tenth of that in HDL3. Glycerol did not affect LCAT activity in both LDL and HDL3 up to 10mM. Palmitic acid did not inhibit cholesterol esterification in LDL up to 5mM but did inhibit cholesterol esterification in HDL3. The inhibition of cholesterol esterification by PA increased almost linearly up to 2.5mM and the inhibition rate of cholesterol esterification was more than 80% at 2.5mM. Linoleic acid and LL had strong inhibitory effects on cholesterol esterification in both LDL and HDL3. The inhibition of cholesterol esterification by LA and LL reached the maximum at the concentration of 1.0mM and the inhibition rate was more than 90%.
