Background: Neonatal complications such as chronic lung disease(CLD) could be related to an imbalance between oxidant load and antioxidant defenses. Parenteral multivitamin (MVI) preparations are an important source of peroxides, but they contain free radical scavenging molecules. In cells, peroxides and hyperoxia affect, either directly or by free radical formation the metabolism of prostaglandins (PG) and glutathione (GSH), 2 markers of oxidant challenge. In a whole organism, MVI could modify GSH metabolism if it had radical scavenging properties, and PG if peroxides were bioavailable.

Hypothesis: MVI contributes to the oxidant load received by immature infants.

Methods: One day old guinea pig pups, a recognized model of CLD, receiving intravenous 5% dextrose (240 mL/kg/d) were assigned to 3 groups: a) control (n=8); b) 1% MVI (n=5); c) H2O2 (300μM, same as in 1% MVI) (n=5). After 4 days, total glutathione (GSHt), GSH synthetic activity (Synt), glutathionereductase (GSSG-R) and -peroxidase (GPx) activities, andγglutamyl- transpeptidase (γ GT) activity as well as PGI2, PGE2, PGF2α and thromboxane A2 were determined in lung. Glutathione and related enzymes, as well as the increased ratio of (PGE2+PGF2α)/total PG were used as indexes of lung oxidant challenge.

Results: GSHt content was decreased (31%, p<0.05) and associated with a drop (38%, p<0.05) in Synt in animals receiving MVI. The activities of γGT, GPx and GSSG-R did not differ between groups. With MVI as well as H2O2, the PG ratio increased (37 vs 39%) compared to the controls (p<0.05). Since free radicals stimulate GSH synthesis, the observed drop in Synt suggests that MVI had radical scavenging properties. Because, in the lung, oxidation produces an inhibition of catabolism of PGE2 and PGF2α, the change in PG ratio underlines a concomitant peroxide activity of MVI.

Conclusion: Peroxides infused at concentrations encountered in TPN solutions do not stimulate glutathione synthesis. However, they do have detectable biological effects on the lungs of newborn guinea-pigs. Even though MVI has radical scavenging properties, peroxides contaminating MVI are biologically available for oxidation.