Abstract
The activity of ornithine-oxo-acid aminotransferase (OAT) in the liver and kidneys of rats was notably decreased as a consequence of tumor bearing. The decrease in the activity of OAT was closely related to a concomitant decrease in the rate of synthesis of the enzyme in both host tissues, while the rate of enzyme degradation remained unchanged. These results are concluded to be consistent with the proposal that host tissues of tumor-bearing animals may become “dedifferentiated,” and in this example the mechanism of the expression of the dedifferentiation involved the significant decrease in specific enzyme production.