HISTOLOGICAL STUDY ON THE EFFECT OF ZINC OXIDE NANOPARTICLES ON THE PULMONARY ALVEOLI OF THE ADULT MALE ALBINO RATS
Hala Mahmoud Abd El-Mouaty, Heba Said Ramadan*
Departments of Histology & Cell Biology, Faculty of Medicine, Alexandria University and *Medical Biophysics, Medical Research Institute, Alexandria University
Introduction: zinc oxide nanoparticles (ZnO NPs) are widely used in various industrial and commercial applications. The production of ZnO NPs is increasing every year. However, the available toxicological informations are inadequate to assess the potential risk of nano-ZnO.
Aim of the work: to investigate the possible histological changes that might occur in the pulmonary alveoli following intratracheal administration of ZnO NPs and the degree of reversibility of such changes.
Material & methods: ZnO NPs (<50 nm particle size), were prepared and suspended in phosphate buffered saline (PBS). Then the ZnO NPs were characterized. The study was conducted on 30 adult male albino rats that were divided randomly into three equal groups: Group I (control group): rats were intratracheally instilled with 0.03 ml PBS. Group II (ZnO NPs group): rats were intratracheally instilled with ZnO NPs in a dose of 5 mg/kg in PBS and left for 24 hours. Group III (withdrawal group): rats were intratracheally instilled with ZnO NPs as in group II, followed by a recovery period of one month. At the end of the experiment, the animals were sacrificed under anesthesia. Both lungs were dissected out for light microscopic examination using H&E and Gomori's trichrome stains and transmission electron microscopic study.
Results: Histological examination of rats of group II revealed loss of normal alveolar pattern with vascular congestion and extravasation of red blood cells. Many alveoli were collapsed. Marked thickening of the interalveolar septa and cellular infiltration were also revealed. Ultrastructural examination revealed type II pneumocytes with empty lamellar bodies and partial loss of their microvillous border. Some of them further depicted dense nuclei and mitochondria. Desquamated cells and debris were frequently encountered in the alveolar lumina. The withdrawal group revealed apparent improvement of the alveolar tissue with mild residual affection. Lung sections of this group stained with Gomori's trichrome stain showed areas of moderately increased interstitial collagen deposition.
Conclusion: the study suggested that ZnO NPs might affect the pulmonary alveolar tissue and induce a definite inflammatory reaction. Meanwhile, these effects showed good degree of reversibility after withdrawal of ZnO NPs.