VASCULAR THROMBOXANE FORMATION IN HEMOSTASIS MECHANISM - CORRELATION BETWEEN BLEEDING-TIME AND VASCULAR TXB(2) IN A PATIENT WITH CONGENITALPLATELET CYCLOOXYGENASE DEFICIENCY

We encountered a patient with congenital platelet cyclo-oxygenase defi ciency with normal ability to synthesize vascular prostaglandin I-2 (P GI(2)) and thromboxane A(2) (TXA(2)). The patient's peripheral blood m onocytes did not show cyclo-oxygenase (COX) activity, but cultured bon e marrow fibroblasts showed COX activity. To determine the mechanism o f primary hemostasis in this patient, we examined the effect of oral a dministration of aspirin (1 g) on bleeding time and thromboxane B-2 (T XB(2)), 6-keto prostaglandin F-1 alpha (6-keto-PGF(1 alpha)) productio n in the blood emerging from the incision in this patient, The bleedin g time was markedly prolonged by the administration of aspirin, and th is prolongation was associated with the inhibition of TXB(2) in the ef fluent blood, which seemed to be derived from the vessel wall. These f indings suggest that vascular TXA(2) production plays an important rol e in the maintenance of hemostasis.