Alveolar macrophages have greater amounts of the enzyme 5-lipoxygenase than do monocytes.

Alveolar macrophages release greater amounts of leukotriene B4 (LTB4) and 5-hydroxyeicosatetraenoic acid (5-HETE) after A23187 stimulation than do blood monocytes. The mechanisms for this enhanced 5-lipoxygenase activity in alveolar macrophages are unknown. In these studies, we determined whether alveolar macrophages have greater amounts of the enzyme 5-lipoxygenase than do blood monocytes. We confirmed that alveolar macrophages released greater amounts of LTB4 after A23187 stimulation than did equivalent numbers of blood monocytes. In both the presence and absence of A23187, alveolar macrophages had greater amounts of immunoreactive 5-lipoxygenase, determined by Western analysis, on a per cell and a per protein basis than did blood monocytes. The amounts of 5-lipoxygenase enzyme in the cells roughly correlated with the amounts of LTB4 released by both types of cells. These observations suggest that A23187 stimulates alveolar macrophages to release greater amounts of LTB4 and 5-HETE than blood monocytes, in part, due to the greater amounts of 5-lipoxygenase.