EVIDENCE OF MODIFIED LIPOPROTEIN IN THE PLASMA OF WATANABE HERITABLE HYPERLIPIDEMIC RABBITS BY ANION-EXCHANGE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ASSAY

We searched for evidence for the presence of oxidatively modified low density lipoproteins (Ox-LDL) in the plasma of Watanabe heritable hype rlipidemic (WHHL) rabbits using an anion-exchange high-performance liq uid chromatographic (HPLC) method newly developed for the assay of art ificially modified lipoproteins. Various Ox-LDLs were prepared by incu bation of native LDL (N-LDL) from rabbit plasma with 5 mu M CuCl2 for 0, 1, 3 and 24 h, and separated by anion-exchange HPLC method using a DEAE-glucomannan gel column. With an increase in the incubation time, LDL was further oxidized and retained on the DEAE-glucomannan gel. Thi s oxidized LDL migrated faster in the anodic direction in agarose gel electrophoresis, accompanied by an increase in lipid peroxide levels, estimated as thiobarbituric acid reactive substances (TBARS). There wa s a good agreement in the chromatographic and electrophoretic behavior s of the various Ox-LDLs. LDL from WHHL rabbits showed increases in TE ARS levels, electrophoretic mobility on agarose gel electrophoresis an d cholesteryl ester accumulation in mouse peritoneal macrophages compa red to that from normolipidemic Japanese white (JW) rabbits. When LDLs from both animals were compared by the anion-exchange HPLC method usi ng linear gradient or stepwise elution, LDL from WHHL rabbits had a lo nger retention time and was eluted by a higher concentration of sodium chloride. These results suggest that LDL in WHHL rabbit plasma may un dergo mild oxidative modification. (C) 1998 Elsevier Science Ireland L td. All rights reserved.