Superoxide dismutase activity, caeruloplasmin activity and lipoperoxide levels in tumour and host tissues of mice bearing the Lewis lung carcinoma.

Superoxide dismutase (SOD) activity, plasma caeruloplasmin activity and the level of whole tissue and subcellular lipoperoxides have been determined in normal and neoplastic tissues from control and tumour-bearing mice, measurements being made nine, twelve and fifteen days after the inoculation of Lewis lung carcinoma cells. SOD activity of host liver and lung tissues did not vary significantly from those of the control animals. Blood SOD activity of the tumoured animals was markedly elevated on the ninth and twelfth days after inoculation, decreasing to control levels on the fifteenth day. Tumor SOD diminished from activity on the ninth day which was greater than that for control lung to a level significantly lower than that for control lung on the twelfth and fifteenth days after inoculation. The presence of a tumor did not appear to affect plasma caeruloplasmin oxidase levels. The lipoperoxide level of hepatic tissue rose significantly as the tumour progressed. In the lung tissue the lipoperoxides decreased from a level four times higher on the ninth day to one not significantly different from that of the controls. Tumour lipoperoxides were about twice the level of hepatic tissue and of the order of ten-fold greater than those of lung. The level of lipoperoxide in the plasma of tumoured mice did not differ markedly from that of control mice. Assays of lipoperoxide in subcellular fractions of liver, lung and tumour tissue revealed that the elevated lipoperoxide was principally synthesized in the endoplasmic reticulum.