Distribution of CuZn superoxide dismutase and Mn superoxide dismutase in human tissues and extracellular fluids.

Among various human tissues liver had the highest content of both CuZn superoxide dismutase and Mn superoxide dismutase. There were comparatively small differences in CuZn superoxide dismutase among other organs. The Mn superoxide dismutase contents were roughly half as large as the CuZn superoxide dismutase contents. The total amount of CuZn superoxide dismutase in the body was estimated to be 3900 mg. The superoxide dismutase activities of serum and cerebrospinal fluid corresponded to between 0.2-0.3 mg CuZn superoxide dismutase per liter. CuZn superoxide dismutase was apparently the source of the superoxide dismutase activity in cerebrospinal fluid, whereas this enzyme only accounted for about 15% of the serum activity. The superoxide dismutase activities of ceruloplasmin, transferrin and ferritin were very low, 40 000, 350 000 and 330 000 times lower than that of human CuZn superoxide dismutase. These factors contributed very little to serum superoxide dismutase activity. The activity of lymph was more than twice that of serum. Sera from patients with severely impaired renal function or bilaterally nephrectomized had a very high superoxide dismutase activity.