Endogenous thromboxane A2 does not contribute to the contractile response of human umbilical artery strips to 5-hydroxytryptamine.
1. To investigate the possible role of endogenous thromboxane A2 (TXA2) in 5-hydroxytryptamine (5-HT)-induced contraction, human umbilical artery strips were suspended in isolated organ chambers for measurement of isometric force. 2. In endothelium intact strips, arachidonic acid (AA;1 microM) potentiates the contractile response to 5-HT, whereas the response was reduced by indomethacin (INDO;10 microM). De-endothelialized strips showed reduced responses to 5-HT. 3. Arachidonic acid-induced potentiation of the responses to 5-HT was prevented by INDO, and the TXA2 synthase inhibitor dazoxiben (DAZ;1 microM and 10 microM) was without effect on the responses to 5-HT in endothelium intact strips. 4. Taken collectively, these results suggest that, in human umbilical artery strips, the contractile response to 5-HT is at least partly dependent on the 5-HT induced release of an endothelium-derived contracting factor (EDCF), which is a cyclooxygenase metabolite. The lack of effect of DAZ indicates that TXA2 is not the EDCF released during the contractile response of human umbilical artery strips to 5-HT.
De Moraes
S
S
Department of Pharmacology, University of São Paulo, Cidade Universitária, Brazil. sdmoraes@biomed.icb2.usp.br
Cavalcante
M T
MT
Carvalho
J C
JC
Mathias
R S
RS
D016232:Endothelins / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008855:Microscopy, Electron, Scanning; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D011247:Pregnancy; D012701:Serotonin / Q000494:pharmacology*; D013928:Thromboxane A2 / Q000502:physiology*; D013930:Thromboxane-A Synthase / Q000037:antagonists & inhibitors; D014469:Umbilical Arteries / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure
D016232:Endothelins; D004791:Enzyme Inhibitors; D012701:Serotonin; D013928:Thromboxane A2; D013930:Thromboxane-A Synthase