Plasma enzyme levels in the anaesthetised dog during drainage of thoracic duct lymph.

The effect of continuous removal of thoracic duct lymph on plasma activities of creatine phosphokinase (PCK), glutamic-oxaloacetic transaminase (PAST); and lactic dehydrogenase (PLDH), uas examined in pentobarbital-anaesthetised dogs over a 5.5-hour period. PCK and PAST declined relative to levels in control dogs while PLDH was unaltered. Lymph/plasma (L/P) ratios for AST and CPK were greater, and for LDH less, than the L/P ratio for total protein. It was concluded that PCK, and to some extent PAST, are normally maintained by introduction of enzyme, escaping from the intracellular compartment, into the circulating blood via the lymphatic system. PLDH and PAST appear to be maintained principally by introduction of enzyme directly from the intracellular to the plasma compartment.