Measurements of Plasma Glutaredoxin and Thioredoxin in Healthy Volunteers and During Open-Heart Surgery

Thioredoxin (Trx) and glutaredoxin (Grx) are both multifunctional redox-active proteins. In this study, Grx was identified in human plasma by immunoaffinity purification. The affinity-purified material from human plasma displayed a band of 12 kDa identical to recombinant human Grx by Western blotting and its glutathione-dependent reducing activity of β-hydroxyethyl disulfide. Competitive enzyme-linked immunosorbent assays (ELISA) showed that plasma levels (mean ± SD) of Grx and Trx in healthy volunteers (n = 41) were 456 ± 284 ng/ml and 28.5 ± 12.6 ng/ml, respectively. In cardiac surgical patients (n = 17), plasma Grx levels did not significantly change during cardiopulmonary bypass (CPB). In contrast, Trx levels in arterial plasma measured by sandwich ELISA and corrected for hemolysis were elevated during reperfusion of the postcardioplegic heart (p = .0001 at maximum), whereas by competitive ELISA Trx increased during surgical preparation for CPB, but decreased during CPB. When recombinant Trx was oxidized, immunoreactive Trx levels were decreased by competitive ELISA but not changed by sandwich ELISA. These results suggest that oxidized Trx is released into plasma during CPB. There was no significant difference in Trx and Grx levels between arterial and intracoronarial plasma samples, indicating no specific release by the postcardioplegic heart. Trx and Grx may be important components in the plasma defense against oxidative stress.