Quantification of 8-iso-prostaglandin-F_2α and 2,3-dinor-8-iso-prostaglandin-F_2α in human urine using liquid chromatography-tandem mass spectrometry

Quantification of 8-iso-prostaglandin F_2α (8-iso-PGF_2α) has been suggested to be a reliable indicator of lipid peroxidation that may be related to in vivo free radical generation, oxidative damage, and antioxidant deficiency. We have developed a LC-MS/MS method to quantify 8-iso- PGF_2α and its dinor metabolite, 2,3-dinor-8-iso-prostaglandin F_2α (2,3-dinor-8-iso-PGF_2α), in human urine samples. After an initial purification step using an automated C18 solid phase extraction procedure, the urine sample was injected directly into a liquid chromatography (LC) system and detected with tandem mass spectrometry. The detection limit of the assay was 9 pg for 8-iso-PGF_2α and 3 pg for 2,3-dinor-8-iso-PGF_2α with both inter- and intraday variations of less than 12%. The inaccuracies were less than 3% for both analytes at three different levels. The urinary excretion rate of 2,3-dinor-8-iso-PGF_2α was higher than that of 8-iso-PGF_2α, and changed in proportion to the parent compound (R = 0.70, n = 60). Values obtained with this method showed good linear correlation to duplicate 8-iso-PGF_2α measurements performed with GCMS (R = 0.97, n = 15). The mean excretion rates of 8-iso-PGF_2α and 2,3-dinor-8-iso-PGF_2α were significantly higher in smokers than in nonsmokers (0.53 ± 0.37 vs. 0.25 ± 0.15 μg/g creatinine, p = 0.002 for 8-iso-PGF_2α and 8.9 ± 3.8 vs. 4.6 ± 2.6 μg/g creatinine, p = 0.003 for 2,3-dinor-8-iso-PGF_2α, respectively). The excellent accuracy, reproducibility, and high throughput of this method should permit it to be used in large clinical studies and standard clinical laboratories.