ENDOTHELIUM-DEPENDENT POTENTIATION BY COCAINE OF SEROTONIN-INDUCED CONTRACTIONS IN SHEEP FETAL UMBILICAL ARTERY

OBJECTIVE: To evaluate the potential role of the endothelium in cocain e-mediated potentiation of serotonin-induced contractions of fetal ovi ne umbilical artery. METHODS: Umbilical cords were isolated from near- term pregnant ewes (approximately 140 days). Serotonin-induced-dose-de pendent contraction of the umbilical arteries was performed in the pre sence and absence of 3 mu mol/L cocaine. The responses were compared b efore and after removal of the endothelium. RESULTS: Cocaine (3 mu mol /L) potentiated serotonin-induced contractions in the endothelium-inta ct ovine fetal umbilical arteries and shifted the concentration-respon se curve to the left (median effective concentration: 2.69 +/- 0.11 -- > 1.23 +/- 0.14 mu mol/L, P < .01). The maximum response expressed as a percentage of maximum KCl was also significantly increased (167.4 +/ - 12.8 --> 216.2 +/- 16.7, P < .05). Removal of the endothelium abolis hed the potentiation by cocaine of serotonin-induced contractions (med ian effective concentration: 1.35 +/- 0.12 --> 1.51 +/- 0.21 mu mol/L, P > .05). The maximum responses were also the same (201.8 +/- 14.3 -- > 206.4 +/- 16.5). CONCLUSION: The results suggest that, in ovine feta l umbilical arteries, cocaine-mediated potentiation of serotonin-induc ed contractions is endothelium dependent. (C) 1998 by the Society for Gynecologic Investigation.