Estimation of the response of respiratory tracts to a single intra-tracheal introduction of nano- and micro-sized particles of aluminum oxide

Introduction. Nanomaterials are now widely used in science and in various industries; in relation to that, it is truly vital to perform hygienic research to assess exposure to ultra-disperse particles with carcinogenic effects on a human body as such research can help to solve tasks in the preventive medicine sphere.

Data and methods. The experiment was performed on 27 pubescent male Wistar rats (9 animals in each group); the animals were exposed to a single intra-tracheal introduction of suspensions that contained nano-sized and micro-sized aluminum oxide in concentrations of 80.0 ± 0.09 mg/ml. The reference group was exposed to a pure suspension (sterile isotonic saline). To quantitatively assess cellular responses in the respiratory tracts, the authors examined digital images of smears obtained via optical immersion microscopy with a polarizing microscope.

Results. Cytological assessment of bronchi-alveolar lavage in vitro revealed exposure to nano-particles of aluminum oxide to led to a cellular response as of eosinophilic type; exposure to micro-particles of aluminum oxide, as of neutrophilic type. The authors proposed a model that described a relationship between a number of eosinophils and neutrophilic leucocytes in bronchi-alveolar lavage and a surface area of aluminum oxide particles; basing on the model, they detected a trigger value; when obtained values are higher than it eosinophilic responses occurs, and when they are lower, a lymphocytic one. The authors also showed that exposure to nano- and micro-sized particles of aluminum oxide resulted in damage to alveolar macrophages surface; the degree of the damage depended on a specific surface area of particles. The obtained data enrich theoretical knowledge accumulated in nanotoxicology and allow to develop etiologically and pathogenetically grounded preventive activities for workers employed at nanomaterials productions and for people who consume products containing nano-sized particles of aluminum oxide.

Discussion. The authors performed the comparative assessment of responses that occurred in the respiratory tracts of Wistar rats as a response to a single intra-tracheal introduction of micro- and nano-sized particles of aluminum oxide; the assessment results were then summarized and their generalization revealed toxic effects to be produced by the particles depended on their dispersity. The obtained data are well in line with an opinion expressed by some authors that a dispersity factor tends to grow as particles become smaller in their size. Another outcome here could be their greater toxic properties that cause various qualitative and quantitative cytological changes in biological substrates, including bronchi-alveolar lavage.

Conclusions. A single intra-tracheal introduction of a water suspension containing aluminum oxide into Wistar rats causes cellular responses in the respiratory tracts and damage to alveolar macrophages. Character and intensity of detected changes depend on the total specific surface area of effecting particles.