Relaxant effect of nitric oxide and prostacyclin on serotonin-induced vasocontraction of human umbilical artery.
BACKGROUND
We investigated the effect of nitric oxide and prostacyclin, which are endothelium-derived vasodilators, on serotonin (5-HT)-induced vasocontraction, and 5-HT1-serotoninergic receptor mediated relaxation in the human umbilical artery.


METHODS
Serotonin-stimulated vasocontraction was measured in umbilical artery segments treated with and without 1) L-arginine (10(-4) M approximately 10(-2) M), a precursor of nitric oxide synthesis; 2) methylene blue (10(-5) M) and L-NG-monomethyl arginine (LNMA, 2 X 1O(-4) M), which are specific inhibitors of nitric oxide action and nitric oxide synthesis, respectively; and 3) tranylcypromine (2 X 10(-6) M, 2 X 10(-5) M), an inhibitor of prostacyclin synthesis. 4) Vessels were pretreated with M1, an inhibitor of 5-HT2 serotoninergic receptors, and then prostaglandin F2 alpha (9.O X 1O(-7) M). Finally, we measured the 5-HT1, receptor-mediated relaxation induced by 5-HT.


RESULTS
Treatment with L-arginine significantly inhibits 5-HT-induced contraction in a dose-dependent manner. Treatment with methylene blue and LNMA significantly potentiated 5-HT-induced contraction. Tranylcypromine caused no significant changes in 5-HT-induced vasocontraction. 5-HT1 serotoninetic receptor-mediated relaxation was found at higher concentrations of 5-HT (greater than 4.94 X 10(-5) M).


CONCLUSIONS
Our results suggest that nitric oxide may exert a strong relaxant effect on 5-HT-induced vasocontraction compared with prostacyclin in human umbilical artery.
Okatani
Y
Y
Department of Obstetrics and Gynecology, Kochi Medical School, Japan.
Watanabe
K
K
Nakano
Y
Y
Sagara
Y
Y
D001120:Arginine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011464:Epoprostenol / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008751:Methylene Blue / Q000494:pharmacology; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D010975:Platelet Aggregation Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D011247:Pregnancy; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology*; D014191:Tranylcypromine / Q000494:pharmacology; D014469:Umbilical Arteries / Q000187:drug effects* / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects*; D014664:Vasodilation / Q000187:drug effects; D019323:omega-N-Methylarginine
D004791:Enzyme Inhibitors; D008996:Monoamine Oxidase Inhibitors; D010975:Platelet Aggregation Inhibitors; D011985:Receptors, Serotonin; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D012701:Serotonin; D014191:Tranylcypromine; D001120:Arginine; D011464:Epoprostenol; D008751:Methylene Blue