Effect of Horseradish Peroxidase on Mice Lung Capillaries' Permeability

Horseradish peroxidase has been reported to affect capillary permeability in several animal species, but not in mice. Two types of peroxidases, with different enzymatic activity, were used in mice at different doses, and the lung capillaries' permeability to the latter has been investigated. In animals injected with a low dose of a high reactive peroxidase, although a clear histochemical reaction was present in capillar lumina, the reaction product was never found outside capillaries' walls. In animals injected with the higher dose of peroxidase the reaction product was always found in pericapillary spaces and often in alveolar macrophages. It is suggested that peroxidase, in high dose, can also affect lung capillary permeability in mice.