The effect of continuous removal of thoracic duct lymph on plasma activities of creatine phosphokinase (PCK), glutamic-oxaloacetic transaminase (PAST); and lactic dehydrogenase (PLDH), was 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.

No abstract

In pentobarbital-anesthetized dogs, cardiac pacing by an intra-atrial electrode at 240 beats/min resulted in small but significant increases in the plasma activity of glutamic–oxalacetic transaminase, which returned to control values within 30 min. No change in plasma creatine phosphokinase was observed following pacing. Possible mechanisms responsible for the release of tissue enzyme during pacing include an increase in rate of deformation of, and an increase in substrate transport by, the cardiac muscle plasma membrane.