Endothelial thromboxane receptors: biochemical characterization and functional implications

We have identified thromboxane specific receptors in membrane preparations of bovine pulmonary artery endothelial cells using a potent thromboxane specific antagonist, [ 125 I]-PTA-OH in a binding assay. The binding was specific and saturable. Neither thromboxane B 2 , prostaglandin D 2 nor prostaglandin F 2α displaced the ligand (0.1 nM) at concentrations up to 10 μM. However, binding was displaced by IPTA-OH > SQ29548 > U46619. In addition, we observed that thromboxane mimetic U46619 significantly lowered the basal production of prostacyclin and also markedly suppressed bradykinin-stimulated prostacyclin released by endothelial cells. We propose that an important biological effect of thromboxane on vascular endothelial cells may be the suppression of prostacyclin production.