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Clinical Chemistry 43:4 562–568 (1997)

Enzymes and Protein Markers

Antioxidative enzyme activities in human erythrocytes
Helle Raun Andersen,* Jesper B. Nielsen, Flemming Nielsen, and Philippe Grandjean
Reliable and standardized methods are necessary to determine the expression of antioxidative enzymes and their role in maintaining health. In addition, the variability of the enzymeactivities within the general population caused by age, gender, and life-style factors must be described. This study describes methodological conditions that are suitable for analyzing copper–zinc superoxide dismutase (CuZn-SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and glutathione reductase (GR) in human erythrocytes with a high degree of reproducibility. Intervals for the enzymeactivities have been established in a randomly selected population of 220 individuals between 20 and 89 years of age. An age-related decrease was observed in CuZn-SOD and GR activities, whereas no age-related changes were demonstrated for GSH-Px and CAT. The GSH-Px activity was positively associated with the intake of dietary supplements and negatively correlated with tobacco consumption. Thesefactors probably account for the fact that women tended to have higher GSH-Px activity.
INDEXING TERMS: superoxide dismutase • glutathione peroxidase • glutahione reductase • catalase • biological variability

reduced glutathione (GSH), and several antioxidative enzymes.1 The most important enzymatic antioxidants are superoxide dismutase (CuZn-SOD; EC 1.15.1.1), which catalyzes dismutation ofthe superoxide anion (O2 ) into H2O2, which is then deactivated to H2O by catalase (CAT; EC 1.11.1.6) and glutathione peroxidase (GSH-Px; EC 1.11.1.9). GSH-Px also reduces organic peroxides into their corresponding alcohols. GSH-Px uses GSH as a hydrogen donor whereby GSH is oxidized. The regeneration of GSH is catalyzed by glutathione reductase (GR; EC 1.6.4.2). Wide interindividual variationsmay exist regarding antioxidative capacity, thus affecting individual susceptibility against deleterious oxidative reactions. However, very limited information exists concerning the biological variation of antioxidative enzymes in representative population samples. This study presents intervals for antioxidative enzyme activities from a randomly selected population. All enzyme activities exceptCAT were measured by automated methods.

Detrimental effects caused by reactive oxygen species occur as a consequence of an imbalance between the formation and inactivation of these species. Oxidative damage may be involved in the pathogenesis of major diseases such as cancer, atherosclerosis [1], and certain neurological disorders [2]. Inactivation and removal of reactive oxygen speciesdepend on reactions involving the antioxidative defense system. The capacity is determined by a dynamic interaction between individual components, which include vitamins A, E, and C, -carotene,

Materials and Methods human subjects The sample group consisted of 220 individuals (110 women and 110 men) randomly selected from the Danish central registry of residents by using the following criteria:20 men and 20 women in each age decade between 20 and 89 years, half of them residing within the city and the other half within rural communities. No exclusion criteria were used. Participants were included consecutively, after signing an informed consent form, until their respective subgroups were filled as described in a previous study [3]. The overall response and participation rates were70% and 31% respectively. The participation rate was particularly low in the two oldest age decades (6% and 19%), and the anticipated number of subjects was not obtained in
1 Nonstandard abbreviations: GSH, reduced glutathione; CuZn-SOD, superoxide dismutase; CAT, catalase; GSH-Px, glutathione peroxidase; GR, glutathione reductase; DTT, dithiothreitol; Pr, protein; Hb, hemoglobin; INT,...