Measurement of urinary 8-epi-prostaglandin F2α, a novel index of lipid peroxidation in vivo, by immunoaffinity extraction/gas chromatography-mass spectrometry. Basal levels in smokers and nonsmokers

8-Epi-prostaglandin F_2α (8-epi-PGF_2α) is an F₂-isoprostane recently identified as a marker of free radical-catalyzed lipid peroxidation in vivo and potential mediator of oxidative damage. Currently, endogenous 8-epi-PGF_2α is measured by gas chromatography-mass spectrometry after lengthy sample preparation. We extracted and purified 8-epi-PGF_2α in one step from biological samples on immunoaffinity columns prepared with an anti-8-epi-PGF_2α antiserum, raised in our laboratory. Quantitation was done by stable-isotope dilution gas chromatography/negative-ion chemical ionization mass spectrometry, with selected ion recording. Carboxylate anions of the pentafluorobenzyl ester trimethylsilyl ether derivative of 8-epi-PGF_2α and [²H₄]8-epi-PGF_2α were monitored (m/z 569 and 573). Basal urinary excretion of 8-epi-PGF_2α can be accurately and rapidly measured by this method. Under normal conditions rats (n = 30) excreted 2.18 ± 0.68 ng/24 h. In healthy nonsmoking young volunteers, urinary excretion of 8-epi-PGF_2α, measured three times on alternate days, was fairly constant (CV 2-10%). Nonsmokers excreted significantly less 8-epi-PGF_2α than age-matched smokers (8.08 ± 2.3 vs. 18.40 ± 4.77 ng/h/1.73 m²; n = 6; p <0.005), as reported by others using different methods.