Effect of microgravity on antioxidant defense and oxidative stress in rat liver

The influence of microgravity on liver oxidative stress and antioxidant defenses were investigated in 3 groups of Sprague-Dawley rats: flight (F). aboard Space Shuttle flight 63 for 8 days; flight-simulated module (A); and control (C). Animals were injected with 1 mg interleukin-2 (II,-2) /kg body wt or saline (S) 24 h before lift-off. Liver wts in F and A were greater than that in C (P<0.01 ). Liver protein concentration decreased in F vs A (P<0.05). Activities of glutathione (GSH) peroxidase (GPX) and GSH Stransferase were decreased in F and A vs C (P<0.01 ). Catalase (CAT) activity was decreased in F vs A and C (P<0.05). Activities of glutathione reductase and Superoxide dismutase (Cu-Zn SOD and Mn SOD) were unchanged. The relative abundance of mRNA for GPX. CAT. Cu-Zn SOD, and Mn SOD was reduced in F vs A (P<0.05). Cu-Zn SOD and Mn SOD protein contents were lower (P<0.05) in A vs C and F. Concentrations of total glutathione, GSH, and glutathione disulfide decreased with F vs A and C (P<0.01). y-Glutamylcysteine synthase activity was not altered with treatments. γ-Glutamyl transpeptidase activity was increased in F with IL2, but not with S (P<0.01). Lipid peroxidation was greater in F vs A and C (PO.05), whereas IL-2 attenuated this effect in F (P<0.05). These results suggest that microgravity is associated with increased oxidative stress and may down-regulate hepatic antioxidant enzyme activity. mRNA abundance, and GSH content.