The blood samples were centrifuged and the plasma layer extracted
and frozen at 2808C until analysis. Free F2-isoprostanes in plasma were
quantified, after purification and derivatization, using GC/negative ion
chemical ionization-MS with [2
H4]8-iso-prostaglandin F2a as an internal
standard (20). Compounds were analyzed as trimethylsilyl ether
derivatives by monitoring mass-to-charge ratios of 569 and 573 for
endogenous F2-isoprostanes and the [2
H4]8-iso-prostaglandin F2a inter-
nal standard, respectively.