Application of the spin trapping technique in intact animals requires an understanding of the stability and distribution of the spin traps and their spin adducts in vivo. We studied the stability of DMPO in vivo in mice using HPLC and the stability of spin adducts of DMPO by EPR in plasma, whole blood, peritoneal fluid, and homogenized heart tissue of the rat. At 15 minutes after intraperitoneal injection DMPO had similar concentrations in the liver, heart, and blood of the mice and 40% remained in the organs 2 hours after the injection. In contrast, the spin adduct DMPO-OH was short lived, with a half-life of 3.0 minutes in plasma, and was not detectable 1 minute after formation in whole blood and homogenized heart tissue. The carbon centered spin adduct DMPO-CH(OH)CH3 was more stable, having half-lives of 16, 11, 3.6, and 0.79 minutes in plasma, peritoneal fluid, whole blood, and homogenized heart tissue, respectively. The spin adduct DMPO-SO3 was sufficiently stable for the adduct to be observed directly from living mice.
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longer-lived adducts such as DMPO-CH3, will increase the possibility of detecting these short lived radicals. The successful detection of DMPO-SO3 directly from living animal demonstrates that this is a feasible approach. Acknowledgement We thank Prof. Karen Wetterhahn for allowing us to use the HPLC system in her laboratory. This research was supported by NIH grant GM 34250 and used the facilities of the IERC at Dartmouth supported by NIH grant RR-01811.