INFLUENCE OF LIPID PROFILE AND FATTY-ACID COMPOSITION ON THE OXIDATION BEHAVIOR OF RAT AND GUINEA-PIG LOW-DENSITY-LIPOPROTEIN

Low density lipoprotein (LDL) oxidation is one of the first steps prop osed for the development of atherosclerosis. Since lipid profile and f atty acid composition may affect this process, we studied the influenc e of these factors on the oxidation behavior of rat and guinea pig LDL . Marked compositional differences were observed. Thus, the main lipid carried by rat LDL was triglyceride (TG) (35.8 +/- 5.8%, w/w) whereas total cholesterol (TC) represented 23.8 +/- 3.0%. In contrast, guinea pig LDL contained 13.2 +/- 2% of TG and 44.8 +/- 4.5% of TC. Rat LDL contained higher 20:4(n-6) molar percentages than guinea pig LDL. Thio barbituric acid reactive substances (TEARS) production (255 +/- 26 and 137 +/- 13 nmol malondialdehyde/mg prot. for rat and guinea pig LDL, respectively) and the maximum rate of conjugated dienes (CD) formation (485 +/- 93 and 77 +/- 11 nmol CD/min/mg protein for rat and guinea p ig LDL, respectively) showed that rat LDL are less resistant to oxidat ion in vitro than guinea pig LDL. The higher oxidation rate of rat LDL seems to be related to its lipid profile, mainly to the high proporti on of TG, and to the high content of 20:4(n-6), which is one of the fa tty acids most prone to oxidation. (C) 1998 Elsevier Science Inc.