Kinetics of pulmonary superoxide dismutase in interleukin-1-induced oxygen-tolerant rats

We have previously demonstrated that tracheal insufflation of interleukin-1 alpha (IL-1) enhances pulmonary Mn superoxide dismutase (Mn SOD) activity and protects rats against O2 toxicity (M. F. Tsan, C. Y. Lee, and J. E. White. J. Appl. Physiol. 71: 688-697, 1991). In this study, we investigated the kinetics of mRNA, specific (immunoreactive) proteins, and enzyme activities of pulmonary Mn SOD and Cu,Zn SOD in IL-1-induced O2-tolerant rats. At 1 day after IL-1 (5 micrograms) insufflation and O2 exposure, levels of Mn SOD mRNA and specific protein, but not enzyme activity, were markedly elevated. At 2.3 and 7 days after O2 exposure, levels of Mn SOD mRNA, specific protein, and enzyme activity were all increased in IL-1-treated animals. In contrast, in control rats at 2.3 days after O2 exposure, level of Mn SOD mRNA was markedly elevated, whereas levels of specific protein and enzyme activity were decreased. Levels of pulmonary Cu,Zn SOD mRNA, specific protein, and enzyme activity were unchanged in control and IL-1-treated rats, except that in IL-1-induced long-term O2-tolerant rats (7 days after O2 exposure), they were all increased. Since at 7 days after IL-1 insufflation, normoxia-exposed rats did not show increased levels of pulmonary Mn SOD or Cu,Zn SOD mRNA, the increased levels of pulmonary SOD seen in IL-1-induced long-term O2-tolerant rats are, at least in part, due to the effect of O2 exposure.