ENDOTHELIAL MODULATION OF VASCULAR TONE AND 5-HYDROXYTRYPTAMINE-INDUCED RESPONSES IN HUMAN CHORIONIC ARTERIES AND VEINS

1. In vitro studies were undertaken to evaluate the potential role of endothelium through release of vasodilators compounds on basal tension and on vasoconstrictor response induced by 5-hydroxytryptamine (5-HT) in chorionic arteries and veins rings from normotensive gestants. 2. N-omega-nitro-L-arginine (100 mu M) and methylene blue (10 mu M) incre ased significantly the basal tension in chorionic arteries but not in veins. However, indomethacin (10 mu M) inhibited the basal tension in both kinds of vessels. 3. The sensitivity to 5-HT was significantly lo wer in placental arteries than in veins. Removal of endothelium increa sed the sensitivity of placental arteries to 5-HT in 2.2-fold; however , in veins denudation had no significant effect. 4. N-omega-nitro-L-ar ginine potentiated the 5-HT-induced tone in both types of vessels, but the increase of contraction was greater in chorionic arteries than in veins. However, indomethacin decreased the 5-HT-induced contractions in arteries and veins. 5. These results indicate that NO is more impor tant than vasodilators prostanoids in the control of vascular tone and in 5-HT-induced placental contractile response.