Determination of dynamic thiol/disulphide homeostasis in children with tetralogy of Fallot and ventricular septal defect.

Oxidative stress may contribute to the pathogenesis of congenital heart defects, but the role of dynamic thiol/disulphide homeostasis has not been evaluated. The objective of this study was to assess whether there are changes in thiol/disulphide homeostasis and nitric oxide levels in children with tetralogy of Fallot (TOF) and ventricular septal defect (VSD). A total of 47 children with congenital heart defects (24 TOF and 23 VSD) and 47 healthy age- and sex-matched controls were included in this study. Serum total thiol and native thiol levels were measured using a novel automatic spectrophotometric method. The amount of dynamic disulphide bonds and related ratios were calculated from these values. Serum nitric oxide levels were detected using a chemiluminescence assay. We found that the average native thiol, total thiol, and disulphide levels were decreased in patients with VSD when compared with healthy individuals (p < 0.001, p < 0.001, and p < 0.01, respectively). While native thiol levels were decreased (p < 0.01), disulphide levels were elevated in the TOF group (p < 0.05). We observed marked augmentation of disulphide/native thiol (p < 0.001) and disulphide/total thiol ratios (p < 0.01) in the TOF group. However, there was a significant decrease in native thiol/total thiol ratio in patients with TOF. No significant changes in these ratios were noted in the VSD group. We detected significant elevations in serum nitric oxide levels in children with TOF and VSD (p < 0.001 for all). These results are the first to demonstrate that thiol/disulphide homeostasis and nitric oxide are associated with TOF and VSD in children.