Lung Lesions Induced by Intratracheal Instillation of Vanadium Pentoxide Powder in Rats

Abstract

To clarify acute toxicity and histopathological changes in the lung after exposure to V₂O₅ powder, rats (SD, male, n=66) were observed for 4 weeks after an intratracheal administration of V₂O₅ powder (geometric mean diameter 0.31 μm, geomertic standard deviation σ_g=2.19) at three doses (0.88, 3.0, 13.0 mg/kg body weight). The histopathological lung lesions were developed dosedependently, and characterized by exudative inflammation, injury of alveolar macrophages, and swelling and mucous degeneration in the broncho-bronchiolar epithelia. Growth rate of the V₂O₅ powder-instilled rat was also retarded dose-dependently. The V₂O₅ powder used was composed of not coagulated but well dispersed particles consisting of vanadium pentoxide of more than 99.8% (w/w) with vanadium tetraoxide of less than 0.2%. The V₂O₅ powder was found to be 8 times more soluble in an artificial biological fluid “Gamble's solution” than in a pure water. From the present findings as well as those from the related literature, it was inferred that the histopathological lesions induced by the intratracheally instilled V₂O₅ powder are caused not only by the V₂O₅ particles per se but also by vanadium ions dissolved from the particles into the lung fluid.