Effects of phagocytosis of mineral dusts on elastase secretion by alveolar and peritoneal exudative macrophages

Peritoneal exudative and alveolar macrophages secrete a nonlysosomal neutral protease which hydrolyses particulate elastin suspended in agar. A variety of particles were administered to macrophages in culture to determine their effect on the secretion of this elastase. Among the particles were silica, two types of asbestos, and kaolinite--all minerals implicated in the production of lung diseases accompanied by reorganization of connective tissue. Peritoneal exudative macrophages increased their secretion of elastase in response to phagocytosis of all the pathogenic particles examined. The increase, however, was not as great as that observed with latex beads, the most inert particles. Although these same particle types were phagocytized by cultured alveolar macrophages, none of them augmented the elastase secretion of alveolar macrophages above the resting level, and many decreased it. The lessened stimulation of elastase secretion by peritoneal macrophages and the decrease in the resting level of elastase secretion of alveolar macrophages probably reflect the cytotoxicity of the particles.