Studies on lipid peroxides in platelets. II. Effect of aggregating agents and platelet antibody.

Abstract

Abstract Lipid peroxidation was studied in platelets exposed to a variety of aggregating agents and to specific antibody. Human and rat platelets were used either unwashed and suspended in a plasma medium or washed and suspended in an artificial medium. The products of lipid peroxidation were measured as malonaldehyde by reaction with thiobarbituric acid. Neither adenosine diphosphate (ADP) nor epinephrine increased lipid peroxide formation. The presence or absence of aggregation did not influence these results. Ca ++ and Mg ++ caused aggregation and accelerated lipid peroxide formation when incubated for one hour at 37 °C. Thrombin at concentrations of 1 U. per milliliter or greater produced aggregation and rapidly increased lipid peroxidation; this effect was pH dependent. Polystyrene-latex particles induced both strong aggregation and lipid peroxidation. Glutathione (SH) inhibitors, p-chloromercuribenzoate (CMB) and N-ethyl-maleimide (NEM), enhanced lipid peroxidation in washed platelets two- to threefold over that found in the controls. Heterologous antibody agglutinated platelets and stimulated lipid peroxide formation. Reduced glutathione (GSH) and dithiothreitol (DTT) effectively blocked lipid peroxidation produced by thrombin, SH inhibitors, and platelet antibody without inhibiting aggregation. It is concluded that aggregation as such is not a stimulus to increased lipid peroxidation. The acceleration in lipid peroxide formation resulting from exposure of platelets to thrombin, latex particles, or heterologous antibody may participate in the deleterious effect of these substances on platelets.