Effects of colchicine or cytochalasin B on pulmonary macrophage endocytosis in vivo

Pulmonary macrophages defend lung surfaces by ingesting deposited particles. We investigated to what extent this uptake of particles can be modulated in vivo by two drugs, colchicine and cytochalasin B (CytB). 198Au colloidal gold, in isotonic saline carrier fluid, was intratracheally instilled into male Syrian golden hamsters. The uptake of these particles by pulmonary macrophages was measured when the carrier fluid contained only colloidal gold and when this test particle was combined with graded doses of either drug. We found that macrophage uptake of the particles 1 h after instillation was depressed 37% when colchicine was added to the instillate (150 micrograms/100 g BW). Depression of particle uptake was also seen with CytB at 15 micrograms/100 g BW. Experiments with tritiated colchicine and CytB showed that both drugs were rapidly cleared from the lungs early in the 1 h phagocytic period. The effect of intravenous colchicine and CytB on the clearance of intravenously injected gold colloid by the liver and spleen reticuloendothelial system was negligible. The results of these experiments, in conjunction with in vitro effects of colchicine and CytB, provide insight into the components of cell function active in particle uptake in situ.