Lipoxygenase inhibitors alter aggregation and adhesiveness of human blood platelets from aspirin-treated patients.

The influences of arachidonic acid (AA) and of inhibitors of lipoxygenases (eicosatetraynoic acid-ETYA- and nordihydroguaiaretic acid -NDGA-) on platelet aggregation evoked by collagen or adenosinediphosphate (ADP) as well as platelet adhesiveness to collagen of platelet-rich-plasma (PRP) from aspirin-treated patients were explored. ETYA or NDGA (10(-8) and 10(-7) M) clearly diminished the per cent aggregation evoked by collagen or ADP and delayed its onset. On the other hand AA (0.2 mM) enhanced the aggregation and shortened the lag phase evoked by collagen at 1.2 and 2.6 micrograms/ml, but not at 5.2 micrograms/ml. Platelet-collagen adhesion of PRP was significantly reduced by ETYA or NDGA (10(-7) M) and augmented by AA (2 mM). The results strongly suggest that lipoxygenase products of arachidonate metabolism play an important role in promoting the mechanism(s) underlying human platelet aggregation and adhesiveness.