The effect of heparin on Cu 2+-mediated oxidation of human low-density lipoproteins

Abstract

The effect of heparin (HE) on the susceptibility of human low-density lipoprotein (LDL) to Cu 2+-induced oxidation was investigated by monitoring conjugated diene formation. HE did not modify the maximum formation of conjugated diene, but increased markedly the lag phase. The plot of change in oxidation rate vs. time showed that the absolute value of V max was dependent on Cu 2+ concentration and that HE increased the time necessary to reach V max. The value of constant K (the Cu 2+ concentration producing a t lag of twice the minimum value) increased in the presence of HE, whereas the value of t min (the time theoretically required for LDL oxidation at an infinite Cu 2+ concentration) was not substantially affected. These results indicate that HE might play a protective antioxidant effect on LDL, probably affecting both the structural properties of the particle and the amount of Cu 2+ available for the oxidation.