Formation and action of prostacyclin in the isolated human umbilical artery.

The transformation of [1-14C]arachidonic acid by homogenates of human umbilical arteries was studied. The major compound formed was the stable end product of PGI2, i.e. 6-keto-PGF1 alpha (lactol form) as analyzed by gas-liquid chromatography-mass spectrometry. PGI2 was generated by incubating PGH2 with a lyophilized pig aorta microsome preparation. PGI2 concentrations around 10 ng/ml relaxed the human umbilical artery preparation significantly. Formation of PGI2 by umbilical arteries during pregnancy might be a mechanism for regulation of blood flow to the fetus.