Introduction. Today, nanomaterials have far-reaching application prospects in various fields of industry, agriculture, biology, pharmacology, and medicine. Nanoparticles (NPs) of lead compounds, in particular lead sulfide (PbS), in the nanometer range (12.5 nm -100 nm) have become widely used. The human and animal body has a large number of different barriers of regulatory and protective functions for the formation and preservation of intra-organ homeostasis. The main function of hemato-tissue barriers (HTB) is their permeability, which consists of two types: physiological, and when the structure of the barrier elements is disturbed, which leads to the penetration of toxic substances into the blood. Damage of the barrier components structure, as a result of the exposure to harmful substances, leads to their permeability and the occurrence of pathological processes. The nature of the latter depends on the functional properties of different types of barriers, where each of them has its own morphological properties of the substrate. Therefore, the acquisition of medical and biological knowledge about the role of HTB in the processes of permeability of PbS NPs through its pathologically changed structures helps in understanding the mechanism of these processes and changes in the functional properties of barrier elements in terms of their maintenance of homeostasis by morphological features.
The aim of the research is to determine the mechanism of penetration of PbS NPs through pathologically changed structures of the blood-tissue barrier of the dermis in relation to their functional properties of maintaining homeostasis by morphological features.
Materials and methods of research. The object of the study is PbS NPs and male Wistar rats (n=20), which are divided into 3 groups (1 control, 2 experimental). Experimental rats were treated daily (5 days a week) for 1 month (a 3-month experiment) with a colloidal solution of PbS with NP sizes of 12.5 nm and 100 nm at the rate of 0.001 mol/100 g of body weight on intact (excised) skin with an area of 2 cm². Morphological studies were performed using generally accepted and special histological and histochemical methods.
Results. Morphological studies of the structural elements of HTB of the skin dermis revealed swelling of the cytoplasm of the endothelium of capillaries with the presence of small granular crystal-like inclusions in the cytoplasm. Small foci of subendothelial vascular edema were observed, sometimes focal damage to the integrity of the structure of the vascular endothelium (adhesion of blood cells on its surface). Diffuse swelling of the amorphous main substance with a decrease in the activity of glycosaminoglycans and a significant amount of acidic proteins was revealed. The determined morphological changes should be considered as a pathological state of the structure of the HTB elements, which is more significant due to the action of PbS NPs of small sizes (12.5 nm).
Conclusions. The identified histological and histochemical changes in the structures of HTB elements are evidence of a damage of their protective functional properties, which indicates the penetration of PbS NPs through the barrier into the blood and is confirmed by their accumulation in the form of small granular protein inclusions in the target organs (kidneys, liver) and in the endothelium of their blood capillaries.
Keywords: blood-tissue barrier, hemato-tissue barrier (HTB), mechanisms of penetration, lead sulfide nanoparticles, dermis, blood vessels, basement membrane, interstitial gel, glycosaminoglycans, acidic proteins.
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