Figure 2. Plasma glutathione/glutathione disulfide (GSH/GSSG) and cysteine/cystine (Cys/CySS) redox potentials in humans.
Results show that these redox couples are not equilibrated and become oxidized with age [23,32,78]. The lack of equilibration of these systems implied that protein thiol/disulfide systems also exist in a non-equilibrium state, and this was subsequently confirmed (see text). Cross–sectional and longitudinal studies in humans showed oxidation of thiol/disulfide systems with age, suggesting that progressive changes occur due to lifelong interaction of individuals with environment. Eh is the steady-state redox potential calculated from the measured concentrations using the Nernst equation [78].