Histomorphometric changes in the bronchi and lung parenchyma of rats one day after administration of venom from the scorpion Leiurus macroctenus

Abstract

The lungs are one of the target organs affected by scorpion venom. Given the expansion of scorpion distribution ranges and climate change, the likelihood of venomous scorpions appearing in new territories inhabited by humans is increasing. Thus, there is a need for an in-depth morphological study of the delayed outcomes of envenomation by medically significant scorpion species. The aim of the study was to determine histological and micromorphometric changes in the bronchi and lung parenchyma of rats 1 day after administration of Leiurus macroctenus scorpion venom. The experiment involved 10 male Wistar laboratory rats maintained under vivarium conditions and divided into 2 groups: group 1 – control rats (n=5), which received physiological saline, and group 2 – rats which received scorpion venom at a dose of 28,8 μg/ml (n=5). One day after administration of Leiurus macroctenus scorpion venom, the rats were euthanized, lung samples were removed and subsequently fixed in 10 % neutral formalin or 2.5 % glutaraldehyde and 1 % osmium tetroxide, followed by standard embedding in paraffin or an epoxy resin mixture. For histological and morphometric examination of the lungs, sections with a thickness of 4-5 μm were prepared according to a standard method, followed by staining with hematoxylin-eosin and by the Azan Trichrome, as well as semithin sections with a thickness of 1-2 μm followed by methylene blue staining. Microscopy of the obtained specimens was performed using an OLIMPUS BX 41 at magnifications from ×40 to ×1000. Morphometric analysis (alveolar width, alveolar entrance width and alveolar depth, interalveolar septum thickness, and width of the conducting portion of the bronchiole) was performed using the software Quickphoto Micro 2.3. Statistical analysis was performed using the licensed software package “Statistica 6.0” using nonparametric evaluation methods. One day after administration of Leiurus macroctenus scorpion venom, pronounced degenerative-destructive changes were found in the lungs of rats, manifested by areas of interalveolar septal destruction, formation of areas of increased air content, hemorrhages, areas of dys- and atelectasis, foci of interstitial and intra-alveolar edema, and destruction of alveolocytes with the formation of cavities in which tissue detritus accumulated. Against this background, most sections showed an inflammatory reaction with marked interstitial, peribronchial and peribronchiolar infiltration by white blood cells. The bronchioles showed epithelial desquamation, thickening of the muscular layer and narrowing of the lumen, enlargement of the mucous glands and accumulation of mucus in them. Statistical analysis of morphometric parameters showed a significant decrease in alveolar width by 36.84 % (p=0.0032), alveolar entrance width by 40.52 % (p=0.0003), alveolar depth by 23.02 % (p=0.0140), and the width of the conducting portion of the respiratory bronchiole by 22.26 % (p=0.0003) compared with the control group. At the same time, the mean interalveolar septum thickness increased by 20.20 % (p=0.0065). The ratio of alveolar entrance width to alveolar depth and the ratio of the width of the conducting portion of the respiratory bronchiole to alveolar depth did not differ significantly from the control group values. Thus, Leiurus macroctenus venom causes pronounced acute complex lung injury after 1 day, manifested by a combination of alveolar destruction, edematous, hemodynamic and inflammatory changes, and impaired bronchial patency.