Cytotoxicity, Uptake and Dissolution of ²⁴¹AmO₂ Particles in Dog Alveolar Macrophages in Vitro

Abstract

Because alveolar macrophages play a role in the pulmonary clearance of inhaled particles, experiments were conducted to investigate the toxicity of ²⁴¹AmO₂ particles to alveolar macrophages and the role of these macrophages in the dissolution of ²⁴¹AmO₂ particles. Beagle dog pulmonary alveolar macrophages obtained by bronchopulmonary lavage were exposed in vitro to selected concentrations of ²⁴¹AmO₂. Macrophage viability determined by trypan-blue dye exclusion technique and the ability of the alveolar macrophages to phagocytose opsonized sheep red blood cells were the measures of ²⁴¹AmO₂ toxicity. The uptake of ²⁴¹AmO₂ particles was studied as a function of time. In addition, the dissolution of ²⁴¹AmO₂ by macrophages was determined for periods up to 72 h. After 20 h exposure to concentrations of ²⁴¹Am higher than 4·63 kBq/ml, the phagocytic ability of macrophages was reduced, whereas no significant change in cell viability was observed at this concentration. Significant cell killing occurred at concentrations higher than 18·5 kBq/ml. After 72 h in the cultures, 10% of the ²⁴¹AmO₂ was dissolved by the alveolar macrophages. These findings imply that the inhalation of radioactive particles such as ²⁴¹AmO₂ particles might cause a reduction in the alveolar macrophage population in the lungs. In addition, the dissolution of ²⁴¹AmO₂ particles by alveolar macrophages might play a role in the short-term pulmonary clearance of inhaled ²⁴¹AmO₂ particles in the beagle dog.