Resistance of lipoproteins from continuous ambulatory peritoneal dialysis patients to in vitro oxidation

Patients with end-stage renal failure on continuous ambulatory peritoneal dialysis (CAPD) develop abnormalities in plasma lipoproteins that may contribute to their increased risk for atherosclerosis. The oxidative modification of lipoproteins is considered to play a central role in atherogenesis. This study examines the susceptibility to oxidation in vitro of low- and high-density lipoprotein (LDL and HDL, respectively) obtained from long-term CAPD patients. CAPD LDL was less susceptible to copper-mediated protein derivatization (fluorescence) compared with control LDL CAPD LDL and HDL displayed less copper-promoted conjugated-diene production and lipid peroxide generation, suggesting a greater resistance of CAPD lipoprotein lipids to oxidation. Autooxidation during long-term storage was also much lower in CAPD LDL and HDL. However, when 2,2'-azobis(2-amidinopropane) dihydrochloride (ABAP) was used to initiate oxidation, there was no difference in conjugated-diene generation between CAPD and the control. CAPD LDL contained slightly less oxidizable, polyunsaturated fatty acid, but the vitamin E content of CAPD and control LDL was equivalent. Our findings indicate that lipoproteins from uremic patients undergoing long-term CAPD are more resistant to in vitro oxidation than control lipoproteins.