The activities of superoxide dismutases, and the variation of superoxide radicals and hydrogen peroxide contents in the brain and liver tissues, and some of the classic signs of rats administered with either 2, 4-dinitrophenol or arsenate has been investigated. Superoxide dismutase activities were determined either by the method of McCord and Fridovich(1969) or by the method of Crapo et al. (1978). The contents of hydrogen peroxide was determined according to the method of Thruman et al. (1972) The experimental results were summarized as, follows;
1. Body weights of animals administered with 2, 4-dinitrophenol and/or arsenate were decreased, but the rectal temperatures of animals treated rose above the normal when compared with those of control group.
2. Formation of superoxide radicals in the tissues of brain and liver of 2, 4-dinitrophenol treated animals was increased to each :i. 5 and 1. 3 times those of the control group. However, formation of superoxide radicals in the tissues of animals administered with arsenate was not changed in the brain tissues, but significantly decreased in the liver tissues.
3. The contents of hydrogen peroxide was slightly increased in both brain and liver tissues of animals administered with 2, 4-dinitrophenol, but no changes occured in those tissues of animals administered with arsenate.
4. The specific activity of total superoxide dismutase in the brain tissues of animals administered with 2, 4-dinitrophenol was enhanced up to 1.7 times that of the control group, but when treated with arsenate; the specific activity was closed to that of the control group.
5. The specific activities of total superoxide dismutase in the liver tissues of animals treated with 2, 4-dinitrophenol and/or arsenate were 4. 68 and 3. 77, respectively.
6. The activities of Mn-superoxide dismutase in the brain and liver tissues of animals treated with 2, 4-dinitrophenol was increased to 2.2 and 2.0 times as higher as that of the control group, but no significant change in the activity of Cu,Zn-superoxide dismutase was observed, whereas in the case of arsenate treated animals, no changes in the specific activities of Cu,Zn- and -Mn-superoxide dismutase was observed.
These results indicated that an uncouples 2, 4-dinitrophenol which may act on all the sites of oxidative
phosphorylation caused to ;increase the superoxide radicals in the cells, and this might occur at State 4. A parallel increment of the formation of superoxide radicals and Mn-superoxide dismutase activities would´ suggest that the enzyme, especially 1VIn-superoxide dismutase, must be an important factor to protect the mitochondria from the toxicity by superoxide radicals.
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