A significant proportion of F2-isoprostanes in human urine are excreted as glucuronide conjugates.

The measurement of urinary F(2)-isoprostanes is noninvasive and widely used to assess in vivo oxidative stress in humans. Most studies measure urinary F(2)-isoprostanes in the free form; however, many eicosanoids are excreted as urine glucuronide conjugates. Using gas chromatography-mass spectrometry, we examined the extent of glucuronide conjugation of F(2)-isoprostanes in urine collected from healthy men (n = 20) and women (n = 15). Incubation of urine with exogenous glucuronidase led to F(2)-isoprostane concentrations that were approximately 40% higher than untreated samples (P < 0.001). We conclude that a significant proportion of F(2)-isoprostanes in urine are conjugated as glucuronides. Copyright 2010 Elsevier Inc. All rights reserved.