Effects and Interactions of Oxygen and Prostaglandins on the Tone of the Isolated Human Umbilical Artery

Abstract

Prostaglandin E₂ (PGE₂) and prostaglandin F_2α (PGF_2α) were found to be equipotent contractors of the isolated human umbilical artery (HUA) in the concentration range 0.2–40 μg/ml. Prostaglandin E₁ (PGE₁) relaxed HUA at 0.1–3.0 μg/ml, whereas at 10–50 μg/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–>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.