Effects and interactions of oxygen and prostaglandins on the tone of the isolated human umbilical artery.

Prostaglandin E2 (PGE2) and prostaglandin F2alpha (PGF2alpha) were found to be equipotent contractors of the isolated human umbilical artery (HUA) in the concentration range 0.2-40 mug/ml. Prostaglandin E1 (PGE1) relaxed HUA at 0.1-3.0 mug/ml, whereas at 10-50 mug/ml contraction occurred. PGE2 was significantly more potent at a PO2 of 102 mmHg than at 27, 48 and above 400 mmHg. An increase in PO2 per se (27- greater than 400 mmHg) resulted occasionally in minor increases in the tone of the HUA. Such effects of oxygen had a lag period of 10-15 min. It is suggested that an increased formation of prostaglandins in the umbilical artery at birth is a more likely cause of the closure of the vessel than an increase in PO2.