Oxygen promotes contraction by endothelin-1 in human umbilical artery

The influence of oxygen on the contractile response to endothelin-1 in the human umbilical artery was investigated in vitro. Segments of human umbilical artery were suspended in organ baths to record the circular motor activity induced by endothelin-1 at a pO2 of 12 kPascal (kPa) or 45 kPa. Endothelin-1 induced a concentration-dependent contraction which was significantly larger at 45 kPa O2 compared with the contractile response at 12 kPa O2.