Trapping of free radicals with direct in vivo EPR detection: A comparison of 5,5-dimethyl-1-pyrroline-N-oxide and 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide as spin traps for HO. and SO4.-

To spin trap hydroxyl radical (HO.) with in vivo detection of the resultant radical adducts, the use of two spin traps, 5,5-dimethyl-1-pyrroline-N-oxi de (DMPO) and 5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide (DEPMPO) (1 0 mmol/kg) has been compared. In mice treatment with 5-aminolevulinic acid and Fe3+ resulted in detection of adducts of hydroxyl radicals (HO.), but o nly with use of DEPMPO. Similarly, 'HO. adducts' generated via nucleophilic substitution of SO4.- adducts formed in vivo could be observed only when u sing DEPMPO as the spin trap. The reasons for the differences observed betw een DEPMPO and DMPO are likely due to different in vivo lifetimes of their hydroxyl radical adducts. These results seem to be the first direct in vivo EPR detection of hydroxyl radical adducts. (C) 1999 Elsevier Science Inc.