Age-related change in redox state of human serum albumin.

Human serum albumin (HSA) is the mixture of human mercaptalbumin (HMA, reduced form) and human nonmercaptalbumin (HNA, oxidized form). We developed a rapid and concise HPLC system to obtain the clear resolution of HSA into HMA and HNA, using an Asahipak GS-520H column. The mean value of the fraction of HMA (f(HMA)) for healthy young male subjects was 0.76 +/- 0.04 (n = 54). However, the f(HMA, 60-90) value for healthy elderly subjects (where the numbers in brackets indicate the range of ages) was 0.48 +/- 0.06 (n = 183). In healthy elderly subjects, f(HMA) was significantly lower than in healthy young male subjects, indicating that HSA in the elderly becomes more oxidized than in the young subjects. Consequently, we suggest that one of the important functions of serum albumin could be to participate in the maintenance of a constant redox potential in the extracellular fluids, thus securing a certain redox buffer capacity. f(HMA) on HSA might reflect this redox buffer capacity with age.