Vіsnik Naukovih Doslіdžen' (Apr 2018)
STRUCTURAL CHANGES IN MUSCLES OF THE HIND LIMBS OF RATS WITH ACUTE ISCHEMIA (EXPERIMENTAL STUDY)
Abstract
Acute limb ischemia occurs as a result of obturation of the lumen of large arteries due to acute thrombosis or embolism, as well as impaired of vascular patency, caused by trauma or compression (including the use of hemostatic tourniquets). In case of elimination of the acute ischemia and restoration of arterial blood supply to the affected limb arises a multifactorial lesion of tissues both ischemic and distant from the site of damage, known as the reperfusion-ischemic syndrome. The aim of the study – to establish the manifestations of structural changes in muscle fibers and the microcirculatory bed of the skeletal muscles of the hind limbs of rats in case of acute ischemia caused by the application of an arterial tourniquet. Materials and Methods. The histological and morphometric study the tissues of the four-head muscles of the hind limbs of 60 rats under condition of experimental acute ischemia was performed. There were 11 intact animals in the control group. Acute ischemia was caused by application of SWAT (Stretch–Wrap–And–Tuck) rubber bands on the hind limbs of animals, 5–6 mm width, at the inguinal fold level within 2 hours under thiopental anesthesia. During the experiment, all the animals were divided into 5 study groups of 12 rats in each group. The model of the early postischemic period was represented by groups of animals with reperfusion changes on the 1st, 2nd hour and 1st day after removal of the tourniquet, and model of the late postischemic period on the 7th and 14th days respectively. The histological examination was carried out according to standard methods. The surface layers of the four-headed muscle of the hind limb of rats were studied in the middle third of the thigh below the overlapping area of tourniquet. Morphometric examination was determined by the following parameters: the mean diameter of muscle fibers, the mean cross-sectional area of muscle fibers, the average diameter and the area of nuclei of muscle fibers. Quantitative indicators were processed statistically. Results and Discussion. All-round analysis of the obtained data revealed that the pathological changes in muscle tissue were aroused in the early period of the postischemic lesions and increased to the end of the 1st day. Histological examination revealed the following changes in the muscle tissue: disorganization of the structural components of the muscle cells, reduction of the striation, friability, fluffiness and rupture of the muscle fibers, violation of their sinuosity, nonlinear arrangement of the nuclei, appearance of the detached necrotic regions and location of the nuclei in the intercellular space. The most significant edema of the muscle tissue occurred on the 1st day in the third group of rats ((41.73±0.39) μm). The average diameter of the muscle fibers in this group was exceeded by 3.37 % the corresponding index ((40.37±0.54) μm) of the control group (P˂0.05). The average area of the nuclei of the muscle fibers ((64.03±0.08) μm) in the third group was only slightly higher than the corresponding value ((63.95±0.07) μm) of the control group (P<0.05). The detected decreasing in the nuclearytoplasmic ratio in the second (0.047±0.001) and the third (0.047±0.001) groups of rats compared with the corresponding indicator of the control group (0.050±0.001) (p˂0.05) may indicate the decreasing in the cellular nuclear activity in the result of ischemic injury. Conclusions. The results of remodeling of the muscle fibers and the blood vessels of the microcirculatory bed confirm the development of ischemic-reperfusion syndrome in experimental animals. In study of the skeletal muscles of the hind limbs of the white rats after acute ischemia caused by the application of the tourniquet, it was found that the remodeling of the muscle fibers was mainly manifested by edema, homogenization of sarcoplasm, violation of linear arrangement of nuclei in the myocytes and leukocyte infiltration of endoand perimizia, myolysis with the destruction of the sarcolemma and the release of nuclei into the intercellular space. The reactive lesions were developed in the microvessels of all segments and maximally expressed by the end of the 1st day.
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