Histological and Ultrastructural Characteristics of the Vessels of the Left Ventricular Myocardium of Rats With Experimental Diabetes Complicated With Acute Disruption of Cerebral Blood Flow in the Basin of Carotious Arteries

The risk of the heart disease in patients with diabetes mellitus (DM) is known to be 2-3 times higher than in the general population. Severe cardiovascular complications (CVC) are considered to be the main causes of death in patients with With the exception of DM, acute ischemic strokes (“stroke and heart syndrome”) lead to the appearance of CVC. In patients with diabetes, ischemic strokes occur 2-6 times more often than in individuals without diabetes, so it should be expected that such a combined pathology can deepen structural and functional changes in the myocardium and its vascular bed, but this issue remains practically unexplored. Purpose of the work. To study the histological and ultrastructural equivalents of damage to the left ventricular myocardial vessels in diabetes mellitus complicated by acute cerebral circulation disorders. Material and methods. Diabetes mellitus was modeled by a single intraperitoneal streptozotocin injection (Sigma, USA, 60 mg/kg body weight) to two-month-old rats. In six-month-old rats of the control group and DM animals with a glycemia level above 10 mmol/l, a 20-minute occlusion of both carotid arteries with subsequent restoration of blood flow was performed. On the 12th day of the post-ischemic period after euthanasia, the left ventricular myocardium was taken, fixed in a 10% neutral formalin solution and, after appropriate histological wiring, embedded in paraffin, histological sections 10-15 μm thick were made, stained with hematoxylin and eosin, and the histological structure of hemocapillaries was studied using a Biolam Lomo C11 light-optical microscope. For electron-optical studies, the myocardium was fixed in a 2.5% glutaraldehyde solution (pH 7.3-7.4) for an hour, and after the wiring provided for by the method, embedded in a mixture of epoxy resins and araldite. Ultrathin sections were prepared on an ultramicrotome, stained with 1% aqueous uranyl acetate solution, contrasted with lead citrate, and electron transparency, shape, and structure of hemocapillaries were studied by means of transmission electron microscope 125К. All studies were conducted in compliance with the Council of Europe Convention for the Protection of Vertebrate Animals Used for Experiments and Other Scientific Purposes of 18.03.1986, EEC Directive No. 609 of 24.11.1986, and Order of the Ministry of Health of Ukraine No. 690 of 23.09.2009. Results. Histological studies determined profound structural abnormalities in the arteries, arterioles, and veins of the left ventricular myocardium both in diabetes mellitus and after cerebral ischemia-reperfusion. These abnormalities pertain to all layers of the vascular wall: endothelial cells, middle smooth muscle layer, adventitia, and perivascular areas. The Wogenworth index of arteries and arterioles was significantly increased in comparison with the control group animals to approximately the same extent in both simulated conditions. The most profound structural abnormalities in the left ventricular myocardial vessels were found in diabetes mellitus complicated by cerebral ischemia-reperfusion, which caused signs of impaired blood supply to the heart wall. This was confirmed morphometrically: the Vaughnworth index of arteries increased 63% relative to the norm, 15 and 25% relative to the parameters in separately modeled diabetes and ischemia-reperfusion, respectively (p<0.01), which indicates an additive effect of the combined pathology. Electron microscopy in the hemocapillaries of the left ventricular myocardium of rats with diabetes and ischemic-reperfusion brain injury revealed a violation of the thickness of the basement membrane, indistinct nuclear membranes with deep invaginations of the karyolemma, a decrease in the number of nuclear pores, which indicates a low functional activity of the endothelial cell nuclei; in the cytoplasm - a small number of organelles and pinocytotic vesicles and caveolae, which reflects a violation of transcapillary exchange. The most numerous and significant changes in myocardial hemocapillaries were found in the case of DM complicated by carotid ischemia-reperfusion. Conclusions. Diabetes mellitus and cerebral ischemia-reperfusion cause profound disturbances in the histological and submicroscopic organization of the structural components of the arteries, arterioles and veins of the left ventricular myocardium, which indicate impaired transcapillary metabolism. The most numerous and significant changes in myocardial hemocapillaries were found in the case of DM complicated by ischemia-reperfusion.