Rats’ thyroid gland histological and ultrastructural changes 30 days after the experimental thermal injury on the background of NaCl injection

Abstract

Very frequent natural and man-made disasters as well as current military conflicts are accompanied by injuries complicated by acute blood loss, burns and shock of different degrees of severity. Thermal injuries are one of the world modern medicine most urgent medical and social problems including the same in Ukraine. In response to a burn injury a significant number of pathological processes develop in the body which manifestation involves almost all organs and systems, leading to an expressed homeostasis disturbance and adaptative processes disorder. Thyroid gland is the one of the first which receives the alterative influence in conditions of both threshold and suprathreshold thermal exposure. The purpose of the work is to establish histological and ultrastructural changes in the thyroid gland of experimental animals 30 days after thermal skin injury. 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 a 0.9 % saline 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. In the rats’ thyroid gland the presence of complex changes of a destructive, adaptive-compensatory and regenerative nature was established on the 30th day after a skin burn against the background of 0.9 % NaCl administration. These changes indicate a relative organs hemodynamics normalization together with the structure of various diameters vessels walls which creates the basis for the follicular cells typical structure restoration and new follicles synthesis. The expressed osmiophily and thyrocyte nuclei pyknotization, cytoplasm vacuolization and follicle’s lumen cells desquamation are revealed in the gland parenchyma. These are signs of the organ fibrosis which are supported by connective tissue amount in the stromal component increase. The thyroid gland parenchyma and the vessels surrounding it micro- and ultrastructural changes caused by the thermal altering influence have a time-dependent expression which transforms from predominantly destructive to predominantly restorative throughout the 30-day post-burn period. The authors are sure that the detected morphological changes of the gland have a time-dependent reversibility which is important to consider from both the time-course and the quantitative aspects taking into account the pathogenetically based scheme of pharmacocorrection. The 30th day of the post-burn pathological process manifestation characterizes by a certain imbalance in the compensatory, restorative and synthetic processes manifestation as well as in the destructive and decompensatory processes manifestation which gives reason to hope for the thyroid gland functioning restoration together with organs and systems in case of pathogenetically determined pharmacological treatment administration. Taking into account the thyroid gland morpho-functional changes wave-like dynamics the authors believe that sanogenetic mechanisms activation might occurs which will allow to prescribe the complex pathogenetically determined correction assuming the above-mentioned patho- and sanogenetic mechanisms dynamics.