Background: Human serum albumin (HSA) is a mixture of human mercaptalbumin (HMA, reduced form) and nonmercaptalbumin (HNA, oxidized form).
Methods: We have developed a convenient high-performance liquid chromatographic (HPLC) system for the separation of HSA into HMA and HNA, and studied the mercapt<==>nonmercapt conversion (i.e., dynamic change in the redox state) of HSA. Examination of long-term sample preservation temperature on the redox state of HSA is of fundamental importance for analysis of defense systems against oxidants in humans.
Results: The HMA fraction of HSA (f(HMA)) was markedly decreased, i.e., the redox state of HSA samples was more oxidized, when they were kept even at -20 degrees C for 170 days. Moreover, the redox states of five commercial HSA products were analyzed and the results were compared with those for normal control subjects.
Conclusions: Surprisingly, marked decreases in f(HMA) value for all commercial HSA products were observed.