Low level of superoxide dismutase activity in pheochromocytoma

A copper-zinc superoxide dismutase found in the cytosol and intermembrane space of mitochondria, and a manganese superoxide dismutase detected in the mitochondria were determined in pheochromocytomas and normal adrenal tissues. Manganese superoxide dismutase activity in pheochromocytomas was lower than that in the normal adrenal tissues but copper-zinc superoxide dismutase activity was almost identical. The total catecholamine content in pheochromocytomas was greater than that in the normal adrenal tissues, and negative relationships were noted between superoxide dismutase activities and total catecholamine content in pheochromocytomas alone. The low level of manganese superoxide dismutase activity might be a characteristic of pheochromocytomas and the decrease in manganese superoxide dismutase activity may not be attributed solely to a decrease in the amount of mitochondria but to a nonspecific abnormality in mitochondrial enzymes.