AN HPLC AND EPR INVESTIGATION ON THE STABILITY OF DMPO AND DMPO SPIN ADDUCTS IN-VIVO

Application of the spin trapping technique in intact animals requires an understanding of the stability and distribution of the spin traps a nd their spin adducts in vivo. We studied the stability of DMPO in viv o 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 si milar 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 bl ood 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 hea rt tissue, respectively. The spin adduct DMPO-SO3 was sufficiently sta ble for the adduct to be observed directly from living mice.