Objective - To examine the effects of intratracheally administered indium phosphide (InP) and distribution of indium on male Fischer 344 rats. Materials and methods - Rats were intratracheally given 0, 1, 10 or 100 mg/kg of InP with a mean diameter of 0.8 μm and observed for 1 and 7 days. The bronchoalveolar lavage fluid (BALF) was examined biochemically and cytologically. Serum biochemical, hematological and histopathological examinations were done, and the indium concentration in organs and serum was determined. Findings - The number of neutrophils in BALF remarkably increased in a dose-effect manner 1 and 7 days after administration and InP particles were phagocytized in the macrophages. Total protein (TP), lactate dehydrogenase (LDH), total phospholipid (TPL) and total cholesterol (T-Cho) in BALF showed a clear dose-effect relationship 7 days after administration. Indium was detected in the liver and spleen and increased in a dose-related manner on the next day and 7 days after administration. Serum indium was detected in the group given more than 10 mg/kg but did not reveal a dose relationship. Histopathological examination of the lungs showed phagocytized InP particles in the macrophages and the migration of neutrophiles in the alveoli. InP particles remained in the bronchioles and alveoli until 7 days after. No histopathological changes were detected in the liver or spleen . A hematological study did not reveal significant findings. Interpretation - Intratracheally administered InP particles cause pulmonary inflammation and those particles remain in the lower airways for at least 7 days. Phagocytosis of macrophages may contribute to their disposal and distribution to the liver and spleen. Further study is required with particles with a lower toxic activity than InP and with the same particle size as the InP used in this study, to clarify their specific toxicity. Simultaneously longer observation is needed to assess toxicity in the other organs after distribution.
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