Prostacyclin metabolites, in urine or adults and neonates, studied by gas chromatography-mass spectrometry and radioimmunoassay.

Endogenous levels of two metabolites of prostacyclin, 6-keto-prostaglandin F1 alpha (spontaneous hydrolysis product) and 6,15-diketo-13,14-dihydroprostaglandin F1 alpha (enzymatic degradation product) were measured in urine of adults and neonates by gas chromatography-mass spectrometry, using deuterated internal standards. The method comprised extraction of prostanoids by reverse-phase cartridges and purification by silicic acid column chromatography and reverse-and straight -phase high-performance liquid chromatographies. Exogenous 6-keto-prostaglandin F1 alpha and 6,15-diketo-13,14-dihydroprostaglandin F1 alpha added to urine were recovered quantitatively by gas chromatography-mass spectrometry. Endogenous levels of 6-keto-prostaglandin F1 alpha in urine of adults were 0.11 +/- 0.05 (S.D.) ng/ml (n = 12), whereas in urine of neonates the levels were much higher: 1.41 +/- 0.36 (S.D.) ng/ml (n = 5) on the 3rd day of life declining to 0.51 +/- 0.21 (S.D.) ng/ml (n = 5) on the 5th day. 6-keto-prostaglandin F1 alpha was also estimated in both age groups by radioimmunoassay. Urinary levels of 6,15-diketo-13, 14-dihydroprostaglandin F1 alpha in neonates on the 3rd day of life were 2.12 +/- 0.70 (S.D.) ng/ml (n = 4) and declined until the 5th day. In adult urine this metabolite was below the limit of detection (0.20 ng/ml).