MEASUREMENT OF URINARY 8-EPI-PROSTAGLANDIN F2-ALPHA, A NOVEL INDEX OFLIPID-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-isoprosta ne recently identified as a marker of free radical-catalyzed lipid per oxidation in vivo and potential mediator of oxidative damage. Currentl y, endogenous 8-epi-PGF(2 alpha) is measured by gas chromatography-mas s spectrometry after lengthy sample preparation. We extracted and puri fied 8-epi-PGF(2 alpha) in one step from biological samples on immunoa ffinity columns prepared with an anti-8-epi-PGF(2 alpha) antiserum, ra ised in our laboratory. Quantitation was done by stable-isotope diluti on gas chromatography/negative-ion chemical ionization mass spectromet ry, with selected ion recording. Carboxylate anions of the pentafluoro benzyl 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 ur inary excretion of 8-epi-PGF(2 alpha) can be accurately and rapidly me asured 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 da ys, 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 u sing different methods.