Peroxidase and cytochrome oxidase in rat tissues.

The presence of peroxidase in the uterus of the estrogeninjected ovariectomized rat and in the Walker carcinosarcoma No. 256 of rats has been reported previously (1, 2). In view of the fact that both these tissues undergo rapid proliferation, it was thought of interest to survey several other rat tissues to determine whether peroxidase might be generally associated with proliferation. Bancroft and Elliott (3) studied the distribution of peroxidase in animal tissues in 1934. Their analyses, like those of other workers in this field, were complicated by the presence of hemoglobin, which is itself a weak peroxidase. Nevertheless, they thought that their results definitely indicated the presence of peroxidase in lung and spleen tissue. In the present study special methods were devised in order to insure minimal interference with “true peroxidase” activity by hemoglobin and catalase. Parallel studies were also made on the cytochrome oxidase content of the tissues. There appears to be an inverse relationship between the content of peroxidase and cytochrome oxidase. Tissues such as intestine, uterus, Walker carcinosarcoma No. 256, stomach, spleen, and lung, which have relatively high levels of peroxidase are low in cytochrome oxidase; whereas heart, kidney, brain, and skeletal muscle are characterized by the reverse situation.