Lipopolysaccharide induces exposure of fibrinogen receptors on human platelets

The effect of lipopolysaccharide (LPS) on the exposure of platelet fibrinogen receptors was investigated. The results showed that: 1) LPS increased the binding of fibrinogen-gold complexes to platelets and the labels were primarily limited to shape-changed platelets; 2) LPS caused a dose-dependent rise in intracellular Ca2+ concentration in platelets; 3) LPS induced the activation of platelet protein kinase C (PKC) and the phosphorylation of glycoprotein llla (GPllla) which was inhibited by H-7. All these results suggest that stimulation of platelets with LPS causes a conformational change in glycoprotein llb/llla (GPllb/llla) through platelet shape change and/or phosphorylation of GPllla via PKC, which serves to expose the fibrinogen binding sites of GPllb/llla on human platelets.