Effect of infection and endotoxicosis on plasma lactate dehydrogenase isozymes in white rats.

Vertical slab electrophoresis in polyacrylamide gels was used to monitor changes in lactate dehydrogenase (LDH) isozymes in plasma of white rats during bacterial infection and endotoxin poisoning. Peritoneal infection with Francisella tularensis and Salmonella typhimurium and administration of S. typhimurium endotoxin stimulated significant increases in plasma LDH-5. Rates of change in enzyme activity after infection were directly related to size of infecting dose and type of agent employed. Infection with 1 median lethal dose of F. tularensis stimulated both an early, temporary and a prolonged, secondary elevation in LDH-5 activity, whereas salmonellosis, endotoxicosis, killed cells, and latex particles elicited only an initial response of short duration. Changes observed in plasma LDH-5 after exposure to these agents suggest that, as a result of phagocytosis or cell damage, peritoneal leukocytes contribute to early increases in plasma enzyme activity, whereas extensive liver involvement is responsible for high secondary LDH-5 levels during progressive tularemic infection.