Lactic Dehydrogenase Activity in Blood.

1. Lactic dehydrogenase activity is present in the venous serum of normal human adults. Normal activity ranges from 260 to 850 units per ml with a mean value of470 ± 130 units per ml. 2. Venous whole blood hemolysates of normal adults have a lactic dehydrogenase activity varying between 16,000 to 67,000 units per ml with a mean value of 34,000 ± 12,000 units per ml. 3. Alterations in serum lactic dehydrogenase have been studied in a selected group of disease states. 4. Experimental and clinical myocardial infarction are associated with a rise in serum lactic dehydrogenase activity. 5. Lactic dehydrogenase like serum glutamic oxaloacetic transaminase rises in a characteristic fashion following myocardial infarction.