INTRAVASCULAR CYSTEINYL-LEUKOTRIENE FORMATION BY CLOTTING WHOLE HUMANBLOOD - EVIDENCE FROM CLAMPED UMBILICAL VEIN SEGMENTS AND THROMBUS SPECIMENS

We have recently demonstrated that contact activation of the intrinsic coagulation cascade in vitro is accompanied not only by thromboxane ( TX) B2 generation but also by the formation of 5-lipoxygenase-derived cysteinyl-leukotrienes (LT). In our present study we have investigated the effects of the vascular wall on the eicosanoid formation by whole human blood. Incubation of whole human blood in clamped segments of a utologous umbilical veins incubated in oxygenated Tyrode solution led to a time-dependent generation of cysteinyl-LT and TXB2 in the blood s amples. A clear dissociation in the time-dependent production profiles was observed with cysteinyl-LT practically reaching a plateau phase a t 60 min while TXB2 levels increased up to 90 min. In blood samples in cubated in glass tubes for 60 min TXB2 production was about 13 times h igher and cysteinyl-LT formation only about half as much as in the umb ilical vein segments indicating a differential stimulation of both the cyclooxygenase and 5-lipoxygenase pathway of arachidonic acid metabol ism in these experiments. By reverse phase HPLC the immunoreactive cys teinyl-LT were identified as a mixture of LTC4, LTD4 and LTE4. Since t he data were suggestive of intravascular cysteinyl-LT formation in thr ombotic vessels, thrombus specimens from patients with acute deep vein thrombosis of the lower limb were analysed for these compounds by com bined reverse phase HPLC and specific radioimmunoassay. The thrombus s pecimens contained mainly LTC4 and smaller amounts of LTD4 and LTE4 in dicating in conjunction with the preceding data that cysteinyl-LT form ation may occur in human blood during thrombosis in vivo.