The influence of hypoxia on the population density of alveolar macrophages in the lungs of rats.

The population density of alveolar macrophages was measured in the lungs of hypoxic rats, in rats which had recovered from a period of hypoxia, and in untreated controls. Alveolar macrophages were most numerous in hypoxic animals. The recovery group contained fewer macrophages than the hypoxic group but more than the controls. In the hypoxic animals the distribution of alveolar macrophages was not homogeneous either within an individual rat or amongst the group as a whole. This suggests that the increase in their number may be stimulated by the secondary effects of hypoxia rather than by its direct interference with their metabolism.