Magnetometric Evaluation of the Effects of Gallium Arsenide on the Clearance and Relaxation of Iron Particles

Intratracheal instillation of GaAs suspension has been histopathologically shown to induce a diffuse pulmonary response. In the present study, magnetometry was used to evaluate the effects of intratracheally instilled GaAs on the behavior of externally magne-tized iron particles instilled in rabbit lung. Magnetometric evaluation of the effects of GaAs in rabbits dosed with 30 mg or 300 mg/animal showed significant decreased relaxation of iron particles at 1, 3, 7, 14, 21 and 28 days following instillation compared with the controls. Relaxation indicates a rapid decrease of remanent magnetic field following magnetization of the lungs due to random rotation of phagocytized iron particles in macrophages. Clearance of the iron particles was measured by serial determinations of the remanent magnetic field at the end of magnetization estimated from relaxation curves. Clearance was significantly impaired in rabbits exposed to both doses of GaAs at 14, 21 and 28 days after instillation. Dose-effect relationships were observed in both cases. Histological examination of lungs instilled with these doses indicated active phagocytosis of GaAs and iron particles by alveolar macrophages.