Effects of Escherichia coli lipopolysaccharide on the phosphoinositide metabolism and serotonin secretion in thrombin-activated platelets.

Lipopolysaccharide treatment of platelets in basal conditions does not produce any effect on serotonin secretion or on phosphatidic acid synthesis or arachidonic acid release. However, a brief exposure of platelets to endotoxin enhances the thrombin-stimulated activation of these parameters, whereas a more prolonged treatment with lipopolysaccharide impairs thrombin action. The results presented here also suggest that very short-term treatment of platelets with lipopolysaccharide activates the inositol 1,4,5-trisphosphate 3-kinase. The long-term effects of endotoxin could be mediated by protein kinase C activation.