Enzyme and isoenzyme alterations in Friend disease.

The activities of certain enzymes in the tissus of mice infected with Friend virus have been studied. Progressive increases in LDH, G6PDH and 6PGDH have been observed in the spleen and liver concomitant with malignant transformation. Plasma LDH activity was also observed to increase over the period of study, but changes in the isoenzyme distribution probably resulted from contamination of the Friend virus preparation with lactic dehydrogenase virus. The tissue enzyme changes are similar to those observed in human malignancies.