Tandem mass spectrometric quantification of 8-iso-prostaglandin F2α and its metabolite 2,3-dinor-5,6-dihydro-8-iso-prostaglandin F2α in human urine

Whole body synthesis of F2-isoprostanes, a family of cyclooxygenase-independent eicosanoids formed by free-radical catalysed peroxidation, should be best assessed by quantifying their urinary metabolites. Two methods for the quantitative determination of F2-isoprostane metabolites in human urine performing either thin-layer chromatography (TLC) (method A) or high-performance liquid chromatography (HPLC) (method B) prior to GC–tandem MS are described. Method A allows for simultaneous quantification of 8-iso-PGF2α, one prominent member of the F2-isoprostane family, and its major urinary metabolite, 2,3-dinor-5,6-dihydro-8-iso-PGF2α. Mean excretion was found to be 223 and 506 pg/mg creatinine of 8-iso-PGF2α and 2,3-dinor-5,6-dihydro-8-iso-PGF2α, respectively (n=14). A tight correlation existed between the urinary excretion of these two isoprostanes (r=0.86). Method B enables quantification of dinor-dihydro metabolites of various F2-isoprostanes including 8-iso-PGF2α. 2,3-Dinor-5,6-dihydro-8-iso-PGF2α was found to be an abundant dinor-dihydro F2-isoprostane metabolite. Validity of method A was proven by a combination of HPLC with TLC prior to GC–tandem MS analysis. A correlation was observed between the urinary concentrations of 2,3-dinor-5,6-dihydro-8-iso-PGF2α measured by GC–MS and GC–tandem MS (r=0.84).