Endothelium-dependent contraction induced by acetylcholine in the chicken ductus arteriosus involves cyclooxygenase-1 activation and TP receptor stimulation

In numerous vascular beds, acetylcholine (ACh) evokes the simultaneous release of endothelium-derived relaxing and contracting factors (EDRF and EDCF, respectively). We aimed to determine whether ACh evokes the release of an EDCF in the chicken ductus arteriosus (DA) and to identify its nature. Isolated rings DA from 19-d chicken embryos (total incubation: 21-d) were studied in a wire myograph. Low concentrations of ACh (30 nM-1 mu M) elicited a relaxation, which was followed by a contraction at higher concentrations (3 mu M-0.1 mM). Both relaxation and contraction were abolished by removal of endothelium and were sensitive to the antimuscarinic agents atropine and 4-DAMP (M-3-receptor antagonist). ACh-induced contraction was impaired in the presence of the non-selective inhibitor of cyclooxygenase (COX) indomethacin, the selective COX-1 inhibitor valeryl salicylate, and the thromboxane (TX)/prostaglandin (PG) H-2 (TP) receptor blocker SQ-29458, whereas the response was not affected by the selective COX-2 inhibitor nimesulide, the TX synthase inhibitor furegrelate, the H2O2 scavenger PEG-catalase, the nitric oxide synthase inhibitor L-NAME, or the soluble guanylate cyclase inhibitor ODQ. Enzyme immunoassay determined that, under basal conditions, the chicken DA produced PGE(2), PGF(2 alpha) and TXB2 (stable metabolite of TXA(2)). Prostanoid production was inhibited by indomethacin but was not significantly affected by ACh. We conclude that in the chicken DA, stimulation of muscarinic receptors by ACh induces an endothelium-dependent relaxation followed by an endothelium-dependent contraction. The contraction involves COX-1 activation and TP receptor stimulation.