Lipocortin I production by human alveolar macrophages

Lipocortin I, in some cells, may be a potent inhibitor of phospholipase A2 activity. These studies evaluated the relative amounts of lipocortin I in human alveolar macrophages compared with blood monocytes, using a specific polyclonal antibody and the technique of Western analysis. Lipocortin I was detected in all isolates of human alveolar macrophages and had molecular masses of 37,000 and 33,000 D. Corticosteroids increased amounts of lipocortin I in these cells in a dose-dependent manner. This effect was specific for corticosteroids as related steroids had no effect. Blood monocytes, when compared with alveolar macrophages, contained relatively small amounts of lipocortin I. We conclude that lipocortin I is present in relatively large amounts in human alveolar macrophages and that amounts of the protein can be induced by corticosteroids. We further speculate that the relative amounts of lipocortin I within monocytes/macrophages may be a marker of differentiation.