Effect of hyperoxia on oxygen free radical defense enzymes in the lung of zinc-deficient rats.

The effects of hyperoxia and the response of oxygen free radical defense enzymes in the lung and extracellular environment of the lung were measured in Zn-deficient rats. Although lung was the target organ as indicated by the increased lung:body weight ratio in all hyperoxia-exposed rats regardless of dietary regimen, 85% oxygen exposure seemed to impose a stress on the whole animal as indicated by decreased feed intake and body weight in ad libitum-fed rats. Hyperoxia exposure superimposed on Zn deficiency did not further reduce the feed intake or body weight of Zn-deficient rats. After 7 d of hyperoxia exposure, the Zn-repleted and ad libitum-fed groups consistently had increased activity of lung CuZn-superoxide dismutase (CuZnSOD), glutathione peroxidase and catalase; but changes in CuZnSOD activity were not related to lung Cu or Zn concentrations. Although Zn-deficient and pair-fed rats were unable to increase CuZnSOD activity, they had an increased lung Zn concentration compared with their air-exposed counterparts. Hyperoxia exposure also caused an increase in ceruloplasmin activity of pair-fed and ad libitum-fed control rats. We concluded that dietary Zn repletion started at the beginning of 85% oxygen exposure was effective for increasing the activity of the lung oxygen free radical defense enzymes, thus preventing hyperoxia-induced lung damage in Zn-deficient rats.