Morphofunctional Characteristics of the Mouse Small Intestine Mucosa After a sIngle Irradiation with Various Absorbed Doses

Radiation-induced intestinal damage is a typical complication of radiation exposure, it can be caused by various sources of radiation. Clinical treatment today consists of symptomatic supportive therapy, as there are no specific treatment strategies. The main target of radiation damage is the epithelial cells of the mucous membrane of the small intestine. The study of morphological changes and mechanisms of damage to epithelial cells is necessary when developing the model of radiation damage to the intestine for further assessment of the severity of pharmacological correction. The purpose of the work is to provide a morphological assessment to the state of the epithelial tissue in the mouse small intestine mucosa on the 9th day after a single exposure to X-ray radiation at various absorbed doses (6.5, 7 and 7.8 Gy). Materials and methods. The study was performed on sexually mature white outbred male mice weighing 18-22 g (n = 50). Acute radiation sickness was simulated using the RUM-17 X-ray therapy unit. The animals of the three experimental groups (n = 15 each) received a single X-ray irradiation with different absorbed doses of 6.5, 7 and 7.8 Gy, respectively. On the 9th day after irradiation, the material was fixed according to a routine technique for transmission electron microscopy. The analysis of semifine sections was carried out using a Scope A1c light microscope with an Axiocam ERc 5s camera and using the ZEN 2.3 morphometric program with further processing using Microsoft Office Excel 2013. Results. When exposed to radiation with different absorbed doses on the mucous membrane of the jejunum in mice, common morphological features were revealed: a decrease in the height and deformation of the mucous membrane villi; a decrease in the height of enterocytes from 32.03±2.21 µm in intact animals to 22.86±0.51 µm (at 7 Gy); in crypts, the height of epithelial cells had no significant changes; single dividing cells were located along the entire depth of the crypts; an increase in the length of the microvilli in the brush border on the apical surface of enterocytes from 0.89±0.01 µm to 1.46±0.03 µm (at 7.8 Gy) was revealed. Sublethal and lethal doses are characterized by a slight expansion of the basal parts of crypts with profiles of actively synthesizing goblet cells, in the absorbed dose of 6.5 Gy, similar changes are more pronounced. In all animals of the experimental groups, the loose connective tissue of the proper mucous plate is abundantly infiltrated by leukocytes. Epithelial cell extrusion zones are weakly expressed on the apical surfaces of the villi. A sharp decrease in the number of Paneth cells was revealed. Conclusions. On the 9th day after a single exposure to X-ray radiation at absorbed doses of 6.5, 7 and 7.8 Gy, reactive changes in the epithelial tissue of the mucous membrane of the small intestine have a non-specific character. The most pronounced of them were noted at an absorbed dose of 6.5 Gy. A decrease in the absorbing surface of the mucous membrane results in disturbances of its basic function.