[Kinetic characteristics of Cu2+-induced lipid peroxidation in blood plasma and serum]

The aim of this study was to determine the concentration parameters and time-course of copper-induced oxidation in serum and whole blood plasma. We investigated the oxidizability of undiluted and (2-60-fold) diluted whole plasma (prepared with citrate as an anticoagulant) and serum by monitoring the change in the level of conjugated dienes, ketodienes and malondialdehyde in the samples. The kinetic curves of the accumulation of different lipid peroxidation (LPO) products had similar S-shape, but they differed by a number of quantitative parameters--lag-time, time of improvement and the level of maximal rate of oxidation, as well as time of improvement of the maximal accumulation and maximal amount of LPO products. When the LPO products were formed in undiluted plasma and serum, the lag phase of 2-2.5 h for conjugated dienes and ketodienes, and 11-12 h for malondialdehyde was observed. Oxidation profile showed a negligibly short period of inhibition followed by rapid oxidation for all investigated LPO products when plasma and serum were diluted at least 10-fold. The rate of accumulation and amount of LPO products decreased in the following order: conjugated dienes > ketodienes > malondialdehyde. Choice of blood plasma or serum and a dilution factor strongly influenced intensity of copper-induced LPO. Anticoagulant (sodium citrate), that was used by preparation of plasma, possessed an inhibitory action on LPO, due to formation of copper-citrate chelates. Dilution of plasma and serum increased LPO through lowering of influence of water-soluble antioxidants, but action of fat-soluble antioxidants (dissolved in the lipid phase of lipoprotein particles) by was unchanged. These results indicate that measurement of lipid oxidation induced in vitro in the whole plasma or serum might be more relevant model of the lipoprotein oxidation in the blood than the in vitro oxidation of single isolated lipoproteins.