Unique in vivo applications of spin traps

The ultimate goal of in vivo electron spin resonance (ESR) spin trapping is to provide a window to the characterization and quantification of free rad icals with time within living organisms. However, the practical application of in vivo ESR to systems involving reactive oxygen radicals has proven ch allenging. Some of these limitations relate to instrument sensitivity and p articularly to the relative stability of these radicals and their nitrone a dducts, as well as toxicity limitations with dosing. Our aim here is to rev iew the strengths and weaknesses of both traditional and in vivo ESR spin t rapping and to describe new approaches that couple the strengths of spin tr apping with methodologies that promise to overcome some of the problems, in particular that of radical adduct decomposition. The new, complementary te chniques include: (i) NMR spin trapping, which monitors new NMR Lines resul ting from diamagnetic products of radical spin adduct degradation and reduc tion, (ii) detection of (NO)-N-. by ESR with dithiocarbamate: Fe(II) "spin trap-like" complexes, (iii) MRI spin trapping, which images the dithiocarba mate: Fe(II)-NO complexes by proton relaxation contrast enhancement, and (i v) the use of ESR to follow the reactions of sulfhydryl groups with dithiol biradical spin labels to form "thiol spin label adducts," for monitoring i ntracellular redox states of glutathione and other thiols. Although some of these approaches are in their infancy, they show promise of adding to the arsenal of techniques to measure and possibly "image" oxidative stress in l iving organisms in real time. (C) 2001 Elsevier Science Inc.