Sulfhydryl groups are powerful blood antioxidants. In plasma they are mainly present on proteins and in red blood cells (RBC) mainly present as glutathione. Decreased levels of both sulfhydryls have been reported in respiratory distress syndrome in adults and newborns (NRDS). Because oxidative stress plays an important role in the pathogenesis of CLD, we investigated the postnatal changes in both sulfhydryls in this disease.

Methods: Sulfhydryl (SH) and albumin (Alb) levels in plasma, and reduced and oxidized glutathione (GSH and GSSG resp.) in RBC were measured on d 1, 4, 10, 21 and 28 in controls (n = 21) and babies with NRDS (n = 13) or CLD@ (n = 13) (g.a.: 29.3 ± 1.2, 28.6 ± 1.4 and 27.9 ± 1.5 wks resp.).

Results: No differences in SH levels were found between the groups, but on d 28 the SH/Alb ratio was decreased in CLD (p<0.05). This result occurred because the SH/Alb ratio fell on d 28 in CLD (p<0.05), whereas it remained stable in the other groups. No differences in GSH and the GSH/GSSG ratio were found between the groups, except for a decreased GSH level in both NRDS and CLD on d 28. This finding in CLD may be related to increased RBC transfusions. In CLD significant between patient correlations were found between GSSG and maximum FiO2 (r = +0.78, p<0.005) and GSH/GSSG and maximum FiO2 (r = -0.81, p<0.005).

Conclusion: Prolonged exposure to oxygen in preterm babies with CLD results in oxidative damage to SH groups in plasma, and may also produce oxidation of GSH in RBC.