Plasma enzymes in tumor-bearing rats.

The plasma enzymes, lactic dehydrogenase, glutamic oxalacetic transaminase, and malic dehydrogenase, increased pro gressively in tumor-bearing rats. The amount of increase varied markedly with the type of tumor and the site of implantation. A lactic dehydrogenase agent could not be demonstrated in any of these animals. Isozyme patterns indicated the tumor was a significant contributor to the increased lactic dehydrogenase in the plasma of these rats. The plasma lactic dehydrogenase was increased less in animals that bore a tumor contaminated with bacteria. The clearance rate of lactic dehydrogenase was slower than normal in tumor-bearing rats, and it decreased progressively with tumor growth.