Uptake of latex particles by pulmonary macrophages: role of calcium.

The uptake of latex particles by both viable and fixed hamster pulmonary macrophages was calcium and trypsin sensitive. Particle uptake did not stimulate the uptake of 45Ca. However, when 45Ca uptake was stimulated with A23187, particle uptake was inhibited. When cobalt was added with A23187, the uptake of 45Ca was inhibited and particle uptake returned to control levels. A23187, cytochalasin B, and A23187 plus cytochalasin B all reduced particle uptake to the same extent. Although both A23187 and ouabain produced similar changes in the intracellular levels of Na+ and K+, only A23187 inhibited particle uptake. We conclude that extracellular Ca2+ promotes particle-cell binding through its interaction with a trypsin-sensitive receptor in the pulmonary macrophage membrane. In contrast, elevated intracellular Ca2+ levels inhibit particle ingestion but not attachment.