Plasma Enzyme a N D Isoenzyme Changes D U R I N G P E R F U S I O N O F the Isolated P I G Liver

1. Changes in the perfusate activities of aspartate transaminase, lactate dehydrogenase, its ‘LD-5’ component, sorbitol dehydrogenase, ornithine carbamoyltransferase, and the isoenzyme patterns of lactate dehydrogenase and aspartate transaminase, were investigated in eleven perfusions of pig liver with human blood in order to assess liver cell damage during perfusion. 2. The aspartate transaminase values were a sensitive indicator of liver damage provided that, as was usually the case, the degree of haemolysis was small. Appearance on electrophoresis of the mitochondria1 isoenzyme of aspartate transaminase indicated severe liver damage. 3. Measurement of sorbitol dehydrogenase activity was also shown to be a sensitive index of liver cell damage, and had the advantage that haemolysis did not interfere. 4. Measurement of total lactate dehydrogenase activity was unreliable as this largely reflected the degree of haemolysis rather than liver cell damage. However, the isoenzyme pattern of lactate dehydrogenase on electrophoresis distinguished liver cell damage from haemolysis. The chemical determination of ‘LD-5’ was not a sensitive index of pig liver damage as this fraction is found only in low concentration in pig liver. 5. Ornithine carbamoyltransferase was also found not to be a sensitive marker of liver cell damage.