The effects of
hyperoxia on physiological responses, pathological lung lesions detected noninvasively by
proton magnetic resonance imaging (MRI), and the
oxygen free radical defense
enzymes were measured in Cu-deficient rats. Exposure to 85%
oxygen seemed to impose a stress on the whole animal as indicated by two physiological responses, decreased food intake and decreased
body weight of ad libitum-fed rats. However, all rats exposed to 85%
oxygen, including the Cu-deficient group, were able to survive 1 wk of
hyperoxia exposure. The target organ specificity for
hyperoxia exposure was in the lung as indicated by the increased lung:
body weight ratio in all
hyperoxia-exposed rats regardless of dietary treatment. All dietary treatment groups exposed to
hyperoxia had a similar increase in lung:
body weight ratio, but none of the
hyperoxia-exposed rats had MRI-detectable lung damage. After 7 d of
hyperoxia exposure, all dietary treatment groups, including the Cu-deficient rats, had increased activity of lung CuZn-
superoxide dismutase (CuZnSOD), but changes in CuZnSOD activity were not related to lung Cu or Zn concentrations. We propose that the ability to increase CuZnSOD activity is the most important factor of the enzymatic
oxygen free radical defense system for protection against
hyperoxia-induced lung damage detected by MRI. Even though lung Cu concentration was decreased in Cu deficiency, it seems that Cu-deficient rats are still able to increase lung CuZnSOD activity in response to 85%
oxygen exposure.