❙ Johannes Holzinger, Karl Öttl, Seth Hallström, Wolfgang Domej ❙
Oxidation von Albumin unter normobarer Hypoxie Oxidation of Albumin in normobaric hypoxia
SUMMARY Oxidative stress refers to a condition in which the dynamic equilibrium between oxidative compounds and antioxidant defences is shifted towards oxidants with the consequence of severe modification of biomolecules and/or redox dysregulation. Hypoxia at high altitudes causes endogenous oxidative stress that is also of significance in acclimatization processes to high altitudes. Human serum albumin is a quantitatively significant plasma protein and also an important plasma buffer in the sense of acid/base- as well as redox-chemsitry. Albumin (AL) is well suited as an indicator of redox processes in the organism; based on a free thiol group the AL-molecule may reach different levels of oxidation. However, changes of the molecule in the context of hypoxia have been rarely investigated in the past. In the current pilot study the redox status of AL in relation to the long established marker malondialdehyde (MDA) was investigated in healthy voluntary subjects before and after four hours stay in a normobaric hypoxic chamber (altitude equivalent 5000 m). The hypoxic exposure resulted in a slight but significant increase in oxidized AL, while MDA remained largely unchanged. The fraction of human mercaptalbumin (HMA) as the completely reduced form of AL was decreased by 1.6 % from basic values, while non-mercaptalbumin-I (HNA-1) as the slightly oxidized form increased by 1.4 %. In contrast, HNA-2, representing the highest stage of oxidized AL, remained nearly unchanged. Keywords: albumin (AL), mercaptalbumin, non-mercaptalbumin, normobaric hypoxia, hypoxic chamber (HC) ZUSAMMENFASSUNG Oxidativer Stress beschreibt einen Stoffwechselzustand, bei dem das dynamische Gleichgewicht zwischen oxidativen Substanzen und antioxidativer Ab27
