The influence of glutathione and other thiols on human platelet aggregation

The platelet membrane contains sulfhydryl groups which are essential for normal platelet function. Reduced glutathione (GSH) and other thiols such as cysteine and 6-mercaptopurine were found to inhibit human platelet aggregation induced by adenosine diphosphate (ADP), collagen and arachidonic acid. The inhibition of ADP-induced aggregation by GSH (IC50 = 0.61 +/- 0.05 mM) was greater than that by cysteine (IC50 = 13 +/- 1 mM) or 6-mercaptopurine (IC50 = 5.4 +/- 0.2 mM). Two other thiols, dithiothreitol and beta-mercaptoethanol were found to cause platelet aggregation instead of inhibition. The interaction of GSH with the ADP receptor was noncompetitive in nature.