Serial Lactic Dehydrogenase Activity in Plasma of Mice with Growing or Regressing Tumors.

Close correlation has been observed between the serially tested plasma level of a glycolytic enzyme, lactic dehydrogenase, and the growth of several transplanted mouse tumors. The character of the lactic dehydrogenase curve determined by serial blood sampling of the animals during the development of such tumors is found to consist of five separate phases. The first three appear before any visible evidence of tumor growth. Inhibition or regression of tested tumors, induced by therapeutic compounds, was accurately reflected in a corresponding reduction of lactic dehydrogenase activity in the peripheral plasma of the host.