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The activity and distribution of superoxide dismutase(SOD)(EC 1.15.1.1) was observed in liver, kidney, spleen and serum of normal and Sarcoma 180 ascites tumor bearing mouse, tumor cell and ascitic fluid. And also, the activities and isozyme patterns of SOD were compared with those of normal mouse. SOD activity was measured by the method of McCord and Fridovich. The experimental results are summarized as follows; 1. Specific activities of Cu, Zn-and Mn-SOD of normal mouse liver were 8.7±0.3 and 6.5±2.0, respectively. On three weeks after transplantation of Sarcoma 180 ascites tumor cell, specific activity of Cu, Zn-SOD was 7.5±2.3, while Mn-SOD was not detected. 2. Specific activities of Cu, Zn-and Mn-SOD in kidney of normal mouse were 15.5±1.1 and 10.3±1.8, respectively. On three weeks after transplantation, Cu, Zn-SOD was decreased to 13.5±0.4 but Mn-SOD was not changed on its activity. 3. Specific activity of SOD in spleen of normal mouse was lower than other tissues, but three weeks after transplantation of tumor cell, specific activity of Cu, Zn-SOD was increased to 8.9±0.7. The activity of Mn-SOD was not changed, compared with one in spleen of normal mouse. 4. The isozyme patterns of SOD in the liver, kidney and spleen of normal and tumor bearing mouse were not changed within three weeks after transplantation. 5. The activity of SOD was not detected in the serum of normal mouse but only Cu, Zn-SOD was detected in the serum of tumor bearing mouse on six days after transplantation(0.13±0.03). 6. Cu, Zn-SOD of Sarcoma 180 ascites tumor cell which harvested from the mouse on three weeks after transplantation was low(5.1±0.3), and Mn-SOD was not detected. This results suggest that the Sarcoma 180 ascites tumor has lost most of the ability to defend against oxygen toxicity and this ability significantly decreased in the liver and kidney of mouse with Sarcoma 180 ascites tumor.
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