Oxygen availability as a possible limiting factor in LDL oxidation

Kinetic studies of copper-induced LDL peroxidation commonly assume that the availability of molecular oxygen in the reaction media is not a limiting factor. The present study reveals that this assumption is valid only at low LDL concentrations. At high LDL concentrations, accumulation of oxidation products, as monitored spectroscopically under conditions of various oxygen concentrations in the medium, comes to a halt when the oxygen concentration in the solution, as measured by an oxygen electrode, decreases to near zero levels. Bubbling of the oxygen into the solution results in resumption of peroxidation. These results are important with respect to the ex vivo assaying of lipoprotein peroxidation because many previous studies have been conducted with LDL concentrations that corresponded to polyunsaturated fatty acid concentrations in access of the concentration of molecular oxygen. The possible pathophysiological significance of the results of this study has yet to be evaluated.