Lowered superoxide dismutase activity in distant organs of tumor-bearing mice

Solid tumors were induced by implantation of 5 X 10(6) Ehrlich carcinoma cells im into the right flank of 8- to 12-week-old female CBA/J mice. Tumor-bearing mice were killed at 0, 2, 4, 10, or 24 days after im implantation of the tumor cells, and superoxide dismutase (SOD) activities were determined in liver, spleen, kidneys, lungs, and leg muscle. Depressed SOD activities were seen in all organs studied. In liver, spleen, and kidneys, the manganese SOD (MnSOD) activities were depressed at some point after implantation, even though microscopic examination revealed no evidence of metastases in these organs. Cytochrome c oxidase activity was not diminished in any of the tissues studied, indicating that the decline in MnSOD was not due to a decline in the number of mitochondria or to a general decline in mitochondrial enzymes. When the tumor cells were dialyzed against 0.9% saline, the dialysate contained a factor that when injected im also inhibited SOD activity.