ENDOGENOUS THROMBOXANE A(2) DOES NOT CONTRIBUTE TO THE CONTRACTILE RESPONSE OF HUMAN UMBILICAL ARTERY STRIPS TO 5-HYDROXYTRYPTAMINE

1. To investigate the possible role of endogenous thromboxane A(2) (TX A(2)) in 5-hydroxytryptamine (5-HT)-induced contraction, human umbilic al artery strips were suspended in isolated organ chambers for measure ment of isometric force.2. In endothelium intact strips, arachidonic a cid (AA;1 mu M) potentiates the contractile response to 5-HT, whereas the response was reduced by indomethacin (INDO;10 mu M). De-endothelia lized strips showed reduced responses to 5-HT. 3. Arachidonic acid ind uced potentiation of the responses to 5-HT was prevented by INDO, and the TXA(2) synthase inhibitor dazoxiben (DAZ;1 mu M and 10 mu M) was w ithout effect on the responses to 5-HT in endothelium intact strips. 4 . Taken collectively, these results suggest that, in human umbilical a rtery strips, the contractile response to 5-HT is at least partly depe ndent on the 5-HT-induced release of an endothelium derived contractin g factor (EDCF), which is a cyclooxygenase metabolite. The lack of eff ect of DAZ indicates that TXA(2) is not the EDCF released during the c ontractile response of human umbilical artery strips to 5-HT. (C) 1997 Elsevier Science Inc.