The canine thyroid carcinoma cell established in tissue culture was inoculated with a lysed-cell suspension of canine malignant lymphoma. In the current investigation, the activities of 11 selected enzymes of the oxidative and hydrolytic group were studied histochemically. Except for minor variations, the activity of each of the enzymes in the uninoculated cells remained constant throughout the growth period and into the early degenerative stages. The activity of the glycolytic and Krebs cycle enzyme was stronger than the activity of the succinoxidase and electron transport system enzymes. Alkaline phosphatase activity varied less in the older cultures than in the younger ones.

It was concluded that, except for minor variations, the enzyme activity of the canine thyroid carcinoma cell was similar to the activity of other established tumor cell lines in tissue culture.

In the lymphoma-inoculated cultures, enzymatic alterations paralleling morphologic changes were demonstrated. These changes consisted of decreased activity of glucose-6-phosphate, glutamate, and lactate dehydrogenases, cytochrome oxidase, and alkaline phosphatase in the younger cultures, namely 48, 96, 144, and 168 hr. In the older inoculated cultures, 240, 288, and 336 hr, where the morphologic differences were no longer apparent, the only enzymes that continued to show less activity were glucose-6-phosphate dehydrogenase and alkaline phosphatase. The possibility is discussed that these morphologic and enyzmatic changes in the lymphoma-inoculated cells are due to an oncogenic virus effect in the early phase of growth.

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This work was supported by Grants CA08502-04 and C5859 from the NIH, USPHS, and Grant IN-16-G from the American Cancer Society.

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