Smoking and oxidant stress: assay of isoprostane in human urine by gas chromatography–mass spectrometry

Isoprostane (8-epi-prostaglandin F2a) is synthesized non-enzymatically from arachidonate and active oxygen. We examined the relationship of smoking and excretion of isoprostane in urine with gas chromatography–mass spectrometry selected ion monitoring assay and the stable isotope dilution method. Urine isoprostane concentrations were significantly higher in smokers (n=81, 605.24±59.01 ng/mg creatinine) than in non-smokers (n=39, 424.07±70.37 ng/mg creatinine), but concentrations in ex-smokers (n=21, 487.27±98.48 ng/mg creatinine) did not differ significantly from those in the other groups. In smokers, age, the duration of smoking, and the number of cigarettes per day were not correlated with urine isoprostane concentrations. However, urine isoprostane concentrations were negatively correlated with time since quitting in ex-smokers and with age in non-smokers. These results indicate that smoking increases isoprostane concentration in urine and suggest that smoking causes lipid peroxidation by oxidant stress.