Microscopic and morphometric changes in the bronchi and lung parenchyma of laboratory rats three hours after administration of Leiurus macroctenus scorpion venom

Abstract

Scorpionism is a widespread phenomenon occurring in various regions of the world and poses particular danger to elderly individuals and children. Despite numerous cases of scorpion venom exposure in humans, only a limited number of publications describe the clinical picture, especially regarding respiratory system involvement. Even fewer studies address morphological changes in the lungs or bronchi of deceased individuals or laboratory animals, particularly at different time intervals after a scorpion sting. These gaps at the morphological level, even with a relatively well-studied pathogenetic mechanism of scorpion venom action, do not allow for a complete understanding of its toxic effects. Only through comprehensive investigation of the venom is it possible not only to develop effective antivenoms but also to explore its potential as a promising therapeutic agent. The aim of the study was to determine microscopic and morphometric changes in the bronchi and lung parenchyma of rats three hours after administration of Leiurus macroctenus scorpion venom. Ten male rats maintained under vivarium conditions were used and divided into two groups of five animals each: group 1 (control) received physiological saline, and group 2 received scorpion venom at a dose of 28.8 μg/ml. Three hours after administration, the animals were euthanized and the lungs were collected for histological examination. For microscopic and morphometric analysis, 4-5 μm sections (stained with hematoxylin-eosin and Azan Trichrome) and semi-thin sections of 1-2 μm (stained with methylene blue) were prepared. Microscopy was performed at magnifications ranging from ×40 to ×1000 using an OLIMPUS BX 41 microscope. Morphometric analysis was conducted using Quickphoto Micro 2.3 software. Statistical analysis of the results was performed using the licensed software package “Statistica 6.0” with nonparametric methods. Three hours after venom administration, pronounced inflammatory changes developed in the lungs of experimental animals, manifested by massive lymphocytic-neutrophilic infiltration, most intense around medium- and small-diameter bronchi and bronchioles, up to partial destruction of their walls, fragmentation of muscle bundles, and adventitial edema. The interalveolar space was dominated by basophils, eosinophils, and macrophages, indicating a marked inflammatory response. In the parenchyma, areas of distelectasis alternated with emphysematous regions, where focal destruction of interalveolar septa and fluid accumulation were observed. Morphometric analysis demonstrated a decrease in alveolar width, alveolar entrance width, and alveolar depth (p=0.112, p=0.008, and p=0.174, respectively), as well as a statistically significant narrowing of the conducting portion of respiratory bronchioles (p=0.045). A tendency toward redistribution of air between the alveolar and bronchiolar compartments was identified, reflected histologically by changes in morphometric ratios. The obtained data indicate the development of acute inflammatory-destructive lung injury with impaired ventilatory function already at early stages after intoxication. The combination of observed microscopic changes suggests the formation of structural remodeling of the lung parenchyma as early as three hours after venom administration in laboratory animals.