[Morphometric analysis of the rat lung after exposure to xylene vapors]

Pathomorphologic examinations of laboratory animals' respiratory system, carried out within evaluation of chemical substances toxicity, pose many diagnostic obstacles. Usually, pulmonary pathologies are evaluated based on arbitrarily adopted criteria and subjective "feelings" of a pathologist. To objectivize the results of pathomorphologic studies and evaluation of the usefulness of quantitative morphological techniques, morphometric tests of the lungs of rats exposed to m-xylene vapours of 4000 mg/m3 concentration for 1 and 3 months were carried out. Lungs were expanded by intratracheal insufflation of 10% formalin under controlled pressure of 23-25 cm water column. Using the stereological point--counting method, in microscope preparations evaluated was the relative volume of: a) normal and atelectatic lung parenchyma, b) peribronchial lymphatic tissue, c) interstitial inflammatory infiltrations. Pathological changes were presented in form of numbers; findings were analysed statistically with non-parametric tests of Krushal-Wallis and Mann-Whitney. The morphometric techniques demonstrated significant differences in the lungs of xylene-exposed rats, varying with the duration of exposure and applied dose, as compared to control animals.