Remote tumor effects on lactic dehydrogenase of mouse muscle fibers with different glycolytic--oxidative metabolic potentials.

The total lactic dehydrogenase (LD) activity and the isoenzyme pattern were studied in muscles of mice during the progressive growth of a distally transplanted methylcholanthrene-induced tumor. The thigh muscles as a group (a mixture of fibers with different oxidative-glycolytic metabolic potentials), the gastrocnemius muscle (primarily glycolytic), the soleus muscle (predominantly oxidative), the heart (purely oxidative), and the diaphragm (primarily oxidative) were evaluated. The total LD activity increased in muscles with a high glycolytic metabolic potential. In such muscles a significant increase of the muscle type and a significant decrease of the heart type of LD were observed. After 3 weeks of tumor growth the tumor was resected, and the LD activity and isoenzyme distribution returned toward normal values 2 weeks later.