Differential effects of transition metal ions on in vitro lipid peroxidation of human serum and protein precipitated from serum.

Elevated concentrations of lipid peroxidation products in serum have been documented in some common human diseases. In addition, several reports indicate that peroxidative damage of tissues in laboratory animals are enhanced in acute toxicity from transition metal ions. We studied the effects of four commonly encountered transition metal ions in human acute toxicity: copper, iron, mercury and lead on in vitro lipid peroxidation of human sera. Cupric and ferric ions caused a significant increase in lipid peroxidation products while mercuric and lead ions had no effects. Lipid peroxidation products in sera incubated with 1 mM cupric ion were increased by 210-248% following 24 h of incubation and 340-480% after 48 h of incubation, while the increases were significantly lower in the aliquots of same serum pools supplemented with same molar concentration of ferric ions (110-115% after 24 h and 137-141% following 48 h). On the other hand the effects were reversed when lipoproteins coprecipitated with other serum proteins were incubated with cupric and ferric ions. Under such conditions increases of lipid peroxidation products were significantly higher with ferric ions (240% after 24 h and 600% after 48 h) compared to cupric ions (20% following 24 h and 25% following 48 h). Such differential behavior of cupric and ferric ions in promoting lipid peroxidation can be explained with a different degree of binding of such ions with serum proteins.