Inter-relationships between vascular thromboxane and prostacyclin synthesis.

We have measured the effect of various concentrations of arachidonic acid on the rates of synthesis of prostacyclin and thromboxane in human umbilical artery slices. Increasing concentrations of arachidonate increased the rate of thromboxane synthesis, but had no effect on the rate of prostacyclin synthesis. However, in dexamethasone-treated artery slices, arachidonate increased the rate of thromboxane and prostacyclin synthesis. Overall, it was demonstrated that arachidonate can alter the ratio of prostacyclin/thromboxane synthesis in untreated artery slices and, by inference, arachidonate can alter the thrombogenicity of vascular endothelium. A mechanism is proposed to explain the arachidonate-induced changes in the prostacyclin/thromboxane ratio.