The effect of lipopolysaccharide （LPS） on the exposure of platelet fibrinogen receptors was investigated. The results showed that:l)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.