OXYGEN-RADICAL-MEDIATED LIPID-PEROXIDATION AND INHIBITION OF ADP-INDUCED PLATELET-AGGREGATION

The effects of lipid peroxidation on ADP-induced aggregation of washed rat platelets were examined using a oxygen-radical-generating system consisting of H2O2 and ferrous ion. Lipid peroxidation was assessed by measurement of thiobarbituric acid-reactive substances (TBARS). Incubation of the platelets with various concentrations of H2O2 (2-10 mm) in the presence of 10 μm Fe2+ resulted in a decrease of the aggregating capacity and an increase of TBARS value, depending on the concentrations of H2O2. Addition of catalase (0.1 mg/ml) to the incubation medium containing 10 μm Fe2+ and 10 mm H2O2 effectively protected the aggregating capacity, but superoxide dismutase (0.1 mg/ml) did not protect H2O2 Fe2+-induced inhibition of the platelet aggregation. The results of kinetic studies on the platelet aggregation with varying ADP and Ca2+ concentrations suggested that treatment of the platelets with H2O2 Fe2+ causes decreases in the binding affinities of ADP and Ca2+ for the platelets. On the basis of these results, change in the aggregating capacity of the platelets by treatment with H2O2 Fe2+ is discussed in relation to lipid peroxidation. © 1991.