RATS’ THYROID GLAND HISTOLOGICAL AND ULTRASTRUCTURAL CHANGES THROUGHOUT THE EXPERIMENTAL THERMAL INJURY DYNAMICS ON THE BACKGROUND OF HAES-LX 5 % COLLOID-HYPEROSMOLAR SOLUTION INJECTION

Abstract

The urgency of the burn injury problem is determined by frequent thermal injuries of patients of different ages, the complexity and duration of treatment, long-term disability and relatively high mortality. Depending on the area and depth of the lesion, a burn wound causes multiple and long-lasting disturbances in homeostasis, which cause organs and systems dysfunction. We are interested in the intrathyroid changes that occur during thermal burns, as thyroid gland plays one of the leading roles in the endocrine regulation of organisms’ majority functions. When researching the issue of pharmacological correction of thyroid gland damage after a burn injury, we proceed from the classical fundamental concept regarding its pathogenetic validity. Taking into account the known pathogenetic mechanisms of burn disease with consecutive (and sometimes simultaneous) hypoproteinemia and haemoconcentration manifestations, intoxication formation, inflammatory and autoimmune reaction, we came to a conclusion regarding the reasonability of colloid solutions efficacy testing to attempt the pharmacocorrection in case of thyroid gland both structure and function burning. The purpose of the work is to establish histological and ultrastructural changes in the thyroid gland of experimental rats that were injected with colloidal hyperosmolar solution HAES-LX 5 % in the dynamics of skin thermal damage. Experimental studies were conducted on 90 white male rats. Skin thermal burns were simulated using four copper plates application to previously depilated lateral surfaces of the rats’ body for 10 s. Rats were injected with colloidal hyperosmolar solution HAES-LX 5 % into the vena cava inferior during the first 7 days of the post-burn period. Thyroid gland pieces were fixed in a 10 % neutral formalin solution, dehydrated in alcohols of increasing concentration and embedded in paraffin blocks. The prepared sections of 5-6 μm thickness were stained with hematoxylin-eosin. For electron microscopic studies, pieces of the thyroid gland were taken, fixed in a 2.5% glutaraldehyde solution, and postfixed with a 1% osmium tetroxide solution in a phosphate buffer. Semi-thin sections were stained with methylene blue. Ultrathin sections were contrasted with uranyl acetate, lead citrate according to the Reynolds method and studied in a PEM-125K electron microscope. Colloidal hyperosmolar solution HAES-LX 5 % administration within 7 days of the post-burn period to correct the thermal injury effects has an expressed positive effect on burned animals thyroid gland histo- and ultrastructure. A significant improvement of the structural state of the stromal and parenchymal components of the organ and their relative normalization in the late period under the influence of the applied solution was established in the dynamics of the experiment. The colloidal hyperosmolar solution HAES-LX 5 % positive effects were expressed by cellular walls of the vessels and follicles dystrophic and destructive changes reduction the structural components of the organ restoration during the entire period of the study up to the 30th day of the trial. The first signs of the intraglandular environment recovery after colloidal hyperosmolar solution HAES-LX 5 % use were proved to start registered from the 7th day of the post-burn period and were maximally expressed from the 21st day until the end of the experiment. The authors are sure that colloidal hyperosmolar HAES-LX 5 % solution protective action possible mechanism is the generalized catabolic reaction inhibition and the membrane-protective effect development. A complex of colloidal hyperosmolar solution HAES-LX 5 % protective, adaptive, adaptive, compensatory and regenerative effects were realized throughout the 30 days of the post-burn period, which efficacy exceeds the thyroid gland parenchyma and surrounding tissues destructive, decompensatory and necrotic changes. The authors consider the use of colloidal hyperosmolar solution HAES-LX 5 % to be one of the burn treatment regimen components as a restorative therapy drug and secondary cytoprotection aimed at the vascular wall and tissue defects integrity restoring.