In vivo measurement of the redox state.

As part of an aerobic life, we oxidize a large pool of biomolecules to obtain chemical energy. During this process, several intermediates are formed; some are chemically unstable and are referred to as free radicals (FR). FR tend to react quickly with their surrounding biological environment; depending on the nature of the molecule attacked, different reactions can occur, i.e., lipid peroxidation, protein oxidation, or DNA oxidation products. As aerobic life has evolved, antioxidant defense systems against FR have developed. When an imbalance between production of FR (oxidants) and defense systems against them (antioxidants) happens, a situation of oxidative stress occurs. This can lead to irreversible biochemical changes, with subsequent tissue damage and disease. Establishing the involvement of FR in the pathogenesis of a disease has been difficult because of the lack of sensitive and specific methodology to detect them. No ideal biomarkers for in vivo FR-induced damage are available as yet. However, some reliable indices of FR formation are now available, and in some pathologic conditions, evidence is accumulating to show that FR damage might play a functional role. The task for the near future will be to try to simplify the analytical methodology and elucidate the molecular mechanisms underlying the formation, disposition, and kinetics of FR marker molecules.