Magnetometric Evaluation of Toxicity of Gallium Arsenide to Lungs and Alveolar Macrophage

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Gallium arsenide (GaAs) has led to the development of electro-optical devices such as light-emitting diodes and semiconductor lasers. Several reports point to pulmonary exposure to GaAs dust as a potential occupational health hazard. In vivo pulmonary toxicity, immuno toxicity and effects on porphyrin metabolism have been demons trated in animals exposed to GaAs.A rapid decrease in the magnetic field after magnetization of the thorax of animals intratracheally instilled with magnetic particles has been noted and designated as "relaxation". This phenomenon indicates a rapid decrease of remanent magnetic field following magnetization of the lungs due to random rotation of phagocytosed iron oxide particles in macrophages. In the first part of study, delayd relaxation and clearance of iron oxide were observed in rabbits exposed to GaAs.In the latter part of study, alveolar macrophages adhered to glass in the bottom of wells were exposed to iron oxide 60mug with or without GaAs20mug/ml in culture medium. Rapid relaxation was observed in the sample of GaAs free medium, whereas relaxation for the specimen with GaAs was delayd. GaAs impaired relaxation dose-dependently. Since addition of Ga_2O_3 into the medium did not affect relaxation, arsenic is considered affecting relaxation.LDH release from cells, classical test for cellular toxicity, also indicated toxic effect of GaAs on macrophages. Transmission electron micros copy revealed alterations of cell membrane, organelles and nucleus in macrophages exposed to GaAs.In vivo cellular magnetometry appears applicable to evaluate toxicity of chemical substance on phagocytic cells.