Objective:To evaluate the potential role of the endothelium in cocaine-mediated potentiation of serotonin-induced contractions of fetal ovine umbilical artery.
Methods:Umbilical cords were isolated from near-term pregnant ewes (approximately 140 days). Serotonin-induced—dose-dependent contraction of the umbilical arteries was performed in the presence and absence of 3 μmol/L cocaine. The responses were compared before and after removal of the endothelium.
Results:Cocaine (3 μmol/L) potentiated serotonin-induced contractions in the endothelium-intact ovine fetal umbilical arteries and shifted the concentration-response curve to the left (median effective concentration: 2.69 ± 0.11 → 1.23 ± 0.14 μmol/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 abolished the potentiation by cocaine of serotonin-induced contractions (median effective concentration: 1.35 ± 0.12 → 1.51 ± 0.21 μmol/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 fetal umbilical arteries, cocaine-mediated potentiation of serotonin-induced contractions is endothelium dependent.
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