Development of enzyme-linked immunosorbent assay for 8-iso-prostaglandin F2alpha, a biomarker of oxidative stress in vivo, and its application to the quantification in aged rats.

8-iso-Prostaglandin F2alpha (8-iso-PGF2alpha) is one of the isoprostanes that are mainly generated nonenzymatically in vivo from arachidonic acid through free radical-induced lipid peroxidation. To assess oxidative stress in vivo, we developed a quantitative enzyme-linked immunosorbent assay (ELISA) for 8-iso-PGF2alpha. A sensitive calibration curve allowed the quantification of the amounts from 0.23 pg to 98.4 pg with 4.7 pg of 50% displacement in one assay. The ELISA method was applied to the measurement of the plasma levels of 8-iso-PGF2alpha in young rats (4-8 weeks of age) and aged rats (106-123 weeks). The average level of esterified form in the plasma from aged rats was 30.6-fold higher than that in the plasma from young rats, reflecting the enhanced status of oxidative stress in aged animals. In addition, the aged rats exhibited higher levels of this F2-isoprostane esterified to lipids from liver and kidney, suggesting local oxidative injury in specific organs. These results indicate the utility and accuracy of our ELISA for 8-iso-PGF2alpha as a biomarker in vivo to assess systemic oxidative stress in animals or humans as well as oxidative injury at local sites.