We previously reported the detection of a
carbon-centered radical adduct of alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone (
POBN) in the bile of rats acutely poisoned with
Cr(VI) utilizing an electron spin resonance spin-trapping technique. These former studies suggested that the
free radical metabolite was derived from a
polyunsaturated fatty acid. The present studies were undertaken to further characterize this radical adduct and to determine whether its formation is associated with enhanced lipid peroxidation in vivo. This report demonstrates that electron spin resonance (ESR) spectra with hyperfine coupling constants aN of 15.71 G and of 2.90 G were present in bile from
Cr(VI)-poisoned rats. We found out that virtually identical ESR spectra were obtained when authentic
POBN-pentyl radical adducts generated from the reaction of
POBN with either pentylhydrazine or linoleic or
arachidonic acid with
lipoxygenase were added to bile. The hyperfine coupling constants for the
POBN-pentyl radical adducts added to bile were as follows: aN = 15.85 G and = 2.60 G for the reaction between pentylhydrazine and
POBN; aN = 15.72 G and = 2.61 G for the reaction between
arachidonic acid, lipoxygenase, and
POBN; and aN = 15.85 G and = 2. 85 G for the reaction between
linoleic acid,
lipoxygenase, and
POBN. In addition, the formation of this radical adduct was associated with lipid peroxidation as quantified by increases in
F2-isoprostane levels in bile. These studies, therefore, provide additional evidence that acute
Cr(VI)
poisoning is associated with enhanced generation of
F2-isoprostanes in vivo and tentatively identify the radical species that is produced as the
POBN-pentyl radical adduct.