Abstract
Vascular effects of a thromboxane A2 mimetic, U46619, and prostacyclin on human umbilical arteries have been investigated by in vitro perfusions. Administration of U46619 invariably induced vasoconstrictory responses which were found to be dose-dependent and consistently stronger than those observed with other prostaglandins (e.g. PGF2α and PGE2). Infusion of prostacyclin alone did not lead to significant alterations in the arterial perfusion pressure. However, when prostacyclin was introduced after a constriction with U46619 had been established, a transient pressure decrease was observed. When both drugs were introduced simultaneously, the U46619 response was suppressed. This suppression was partial and dependent on the PGI2 concentration.