ROLE OF LIPOPROTEIN BOUND COPPER IONS IN LIPID-PEROXIDATION OF LOW AND HIGH-DENSITY-LIPOPROTEINS

Copper-catalyzed lipid peroxidation (LPO) in low density lipoprotein ( LDL) and two subfractions of high density lipoprotein (HDL2 and HDL3) isolated from human serum was studied. The levels of LPO were estimate d as thiobarbituric acid-reactive substances (TBARS). The amount of TB ARS increased in a time-dependent manner when either LDL, HDL2 or HDL3 (0,4-1,2 mg protein/ml) was Incubated at 37 degrees C during 4 h with phosphate-buffered saline containing CuSO4 (2-80 mu M). The Increase in CuSO4 concentration to some value therewith caused the enhancement of the rate of TBARS formation but the following increase in CuSO4 con centration beyond that value didn't already affect the kinetics of LPO in lipoproteins. It was also shown that the lesser was the concentrat ion of lipoprotein, the lesser CuSO4 concentration was needed to reach maximal rate of TBARS formation. The data obtained point to the versa tility of the mechanism of copper-catalyzed oxidation of low and high density lipoproteins and suggest that the decisive role in the process belongs to copper ions bound to lipoprotein particle.