Endothelial modulation of vasoconstrictor responses to endothelin-1 in human placental stem villi small arteries.
1. The aim of this study was to assess the role of endothelial cells in the modulation of vasocontractile responses to endothelin-1 (ET-1) of human placental vasculature. 2. Isolated stem villi small arteries (diameter = 170-250 microns) were obtained from healthy parturients who underwent caesarean surgery during the 39th week of pregnancy for cephalo-pelvic disproportion. Isometric tension was measured in vascular rings mounted in a myograph system and challenged with ET-1 (10(-12) to 10(-6) M). 3. The vasocontractile response to ET-1 was significantly (P < 0.001) increased in endothelial-denuded (active tension = 1156 +/- 214 mN mm-1) as compared with endothelial-preserved vascular rings (active tension = 458 +/- 48 mN mm-1). This difference was significantly (P < 0.05) but only partly abolished by the NO synthase inhibitor N omega-nitro-L-arginine (L-NOARG, 10(-4) M). 4. In endothelial-preserved rings submaximally precontracted with 5-hydroxytryptamine (10(-6) M), ET-1 (10(-12) to 10(-9) M) induced dose-dependent relaxation (maximum relaxation = 70 +/- 7%) at 10(-9) M, which was followed, at higher doses (10(-8) to 10(-6) M), by a contraction. In contrast, no relaxation was seen in endothelial-denuded rings. The relaxation in rings with endothelium was significantly (P < 0.001) reduced by L-NOARG (10(-4) M. Moreover, it was totally abolished by combined pretreatment with L-NOARG (10(-4) M) and the sulphonylurea glibenclamide (10(-5) M). 5. In conclusion, endothelial cells modulate the vascular responses to ET-1 through the release of NO and a substance acting on the ATP-sensitive K+ channel of smooth muscle of stem villi small arteries from healthy parturients.
Sabry
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S
Laboratoire de Physiologie Respiratoire, CHU Cochin Port-royal Université René Descartes-Paris V, France.
Mondon
F
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Levy
M
M
Ferré
F
F
Dinh-Xuan
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AT
D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001158:Arteries / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D016232:Endothelins / Q000494:pharmacology*; D004727:Endothelium / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D019335:Nitroarginine; D010920:Placenta / Q000187:drug effects*; D012701:Serotonin / Q000494:pharmacology; D014661:Vasoconstriction
D016232:Endothelins; D004791:Enzyme Inhibitors; D019335:Nitroarginine; D012701:Serotonin; D001120:Arginine