Measurement of urinary 8-epi-prostaglandin F-2 alpha, 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-2 alpha (8-ePi-PGF(2 alpha)) is an F-2-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(2 alpha) is measured by gas chromatography-mass spectrometry after lengthy sample preparation. We extracted and purified 8-epi-PGF(2 alpha) in one step from biological samples on immunoaffinity columns prepared with an anti-8-epi-PGF(2 alpha) 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(2 alpha) and [H-2(4)]8-epi-PGF(2 alpha) were monitored (m/z 569 and 573). Basal urinary excretion of 8-epi-PGF(2 alpha) 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(2 alpha), measured three times on alternate days, was fairly constant (CV 2-10%). Nonsmokers excreted significantly less 8-epi-PGF(2 alpha) than age-matched smokers (8.08 +/- 2.3 vs. 18.40 +/- 4.77 ng/h/1.73 m(2); n = 6; p < 0.005), as reported by others using different methods.