A histochemical study of succinic dehydrogenase and cytochrome oxidase in proliferative lesions of the large intestine.

Morphologie histochemical studies of a number of oxidative enzymes in normal mucosa and proliferative lesions of the large intestine of man have previously been reported (15). In these studies, a weak succinic dehydrogenase activity was observed in poorly differentiated carcinoma of the large bowel. This finding is in accord with other investigations in which a low succinic dehydrogenase activity has been found in a variety of malignant neoplasms (11, 1~). However, since a decrease in activity of this enzyme also occurs in rapidly proliferating nonmalignant tissue, such as regenerating liver (7, 8, 14), it is apparent that the metabolic change it reflects is not specific for malignancy. In contrast to the low succinic dehydrogenase activity of poorly differentiated carcinoma of the large intestine, epithelial components with high as well as low activities of this enzyme were found to be present in well differentiated malignant glands of this anatomic site (15). Similarly, in benign proliferative lesions of the large bowel, epithelia with quite marked differences in succinic dehydrogenase activity were observed in specific components of these tissues. In some instances, the weakly reacting benign elements showed as little or even less activity than tha t found in malignant tissue. In the present report, the results of further investigations of succinic dehydrogenase activity in proliferative lesions of the large intestine are presented. I t will be shown tha t there is a decrease in the activity of this enzyme in elements of all prolifcrative lesions studied. This decrease in enzyme activity would appear to reflect an aspect of altered metabolism common to both benign and malignant proliferative processes of the mucosa of