Experimental manganese lymphadenopathy in guinea pigs

Experimental manganese lymphadenopathy was produced by guinea pigs by intratracheal inoculation of manganese dioxide (50 mg/300 g body weight) and histopathologic changes in the tracheobronchial lymph nodes were studied up to 180 days. There was slow extracellular transport of manganese dust into the nodes, which did not provoke any significant reaction at early periods. However, at later periods the nodes exhibited a significant increase in the density of dust particles and the reaction consisted of phagocytosis, degeneration of dust laden macrophages, slight proliferation of fibroblasts, together with some reticulinosis corresponding to deposits of dust particles. The significance of these findings have been discussed from the chronic toxicity viewpoint.