Lipoxygenase products: leukotrienes C4, D4, A4's breakdown products and 12-HPETE influence platelet aggregation in vivo.

Clinical and pathological observations of diseases concomitant which leukotriene release show consistently an involvement of platelet activation. This effect was hitherto believed to be due to tissue trauma. The aim of the present study was to elucidate whether lipoxygenase products such as leukotrienes C4, D4, 12-HPETE and the breakdown products of leukotriene A4 have a direct pro-aggregatory property of their own. Platelet aggregation was induced by intravascular excitation of fluoresceiniso-thiocyanate-dextran in arterioles of the hamster cheek pouch. "Time to aggregate appearance" was assessed prior and after parenteral application of the studied compounds. LTA4's breakdown products were found to have anti-aggregatory properties, whereas LTC4, D4 and 12-HPETE enhanced platelet aggregability.