Regional difference of endothelium-dependent contractility in human umbilical artery

To investigate whether vascular reactivity of the umbilical artery influences differences in Doppler waveform depending on the sampling site along the cord, we studied a regional difference of endothelium-dependent vascular contractility in human umbilical artery using mechanical responses to the quick stretch of vascular smooth muscle strips. The umbilical artery resistance index (RI) values for the fetal end were significantly higher than those for the placental end. In endothelium-intact strips, stretch-induced contraction of the umbilical artery appears to decrease from the fetal to the placental end of the umbilical artery. No significant differences were noted between strips from the two locations when endothelial cells were rubbed, indicating that this regional difference is related to endothelial cell function. Indo-methacin decreased the stretch-induced contraction of endothelium-intact strips, but tetrodotoxin did not affect this association, suggesting that arachidonic acid metabolism via the cyclooxygenase pathway contributes to modulation of human umbilical artery responsiveness to stretch. These findings suggest that the difference in Doppler waveform of the umbilical artery depending on the sampling site is related to differences in vascular resistance that result from endothelium-related function.