Neutrophil myeloperoxidase concentration: changes with development and during bacterial infection

In experimental animals, the quantity of myeloperoxidase (MPO) in a volume of whole blood, and the neutrophil concentration in that same volume, were determined and the results expressed as units of MPO (10(-7))/neutrophil. Two situations are reported in which the concentration of MPO/neutrophil was found to change; during the growth and development of animals and during bacterial infection. Premature and newborn rats had only 25% of the MPO/neutrophil found in adults. One to three wk olds had 50% of the adult enzyme concentration. During fatal bacterial infection, MPO/neutrophil fell rapidly, often to undetectable levels, but during sublethal infections, following a 24-h lag period in adults and a 48-h lag in neonates, the concentration increased to twice normal.