Funding Acknowledgements Type of funding sources: None. Prolonged hypoosmolar overhydration causes a volume overload necessitating cardioprotectors together with a complex of measures aimed at stabilizing the water and electrolyte balance. The content of water and electrolytes in the human body changes throughout life, so the body's response to the disorder of water and salt balance may be different depending on age. The fluid overload positively correlates with adverse outcomes in critically ill patients. One of the main tasks of modern cardiology is to find the means of leveling the influence of adverse factors on myocardium in different aged patients. The aim of our study was the determination of morphological changes in the myocardium of old laboratory animals under the influence of severe hypoosmolar hyperhydration and attempt to correct the identified changes by means of meldonium. Materials and methods The experiment was conducted in accordance with the "European Convention of the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes" (Strasbourg, 1986). 18 rats at the age of 22 months were divided into 3 series: 2 experimental and 1 control (6 in each). Animals of the first experimental series were modeling severe hypoosmolar hyperhydration by introduction of 10 ml distilled water three times a day through a tube during 25 days. Animals ate boiled unsalted food and were injected a synthetic analogue of antidiuretic hormone "Minirin" (Ferring) with drinking water 2 times a day at a dose 0.01 mg. In addition, the rats of the second experimental series were injected with meldonium intraperitoneally at a dose of 50 mg/kg once a day throughout the entire experiment. The animals of control series received normal drinking water and food and were injected the "Mynyrin"(Ferring) twice a day at a dose of 0.01 mg, considering the potential effects of vasopressin on the cardiovascular system. We measured the diameter of cardiomyocytes (DCMC) of both ventricles, the relative amount of cardiomyocytes (RACMC), connective tissue (RACT), and vessels (RAV), stromal-parenchymal ratio in the ventricles by the formula (RACT+RAV)/RACMC. Results In myocardium of rats administered meldonium, only isolated stromal hemorrhage are noted, while in myocardial samples of the first experimental series there are numerous hemorrhages. DCMC of left ventricle and DCMC of right ventricle are greater than control at 13.18% (p<0.0001) and 12.27% (p<0.0001) respectively. RAV does not change. RACT of left ventricle and RACT of right ventricle increase respectively by 3.72% (p=0.0060) and 5.23% (p <0.0001). RACMC of right ventricle is smaller than the control parameter by 0.63% (p = 0.0015). Conclusion In old animals, meldonium improves the vascular component of the myocardium. However, we have not found the positive effect of the drug on other studied parameters.

中文翻译：

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用美屈宁对动物实验模型的心肌变化进行校正

资金确认 资金来源类型：无。长时间的低渗过度水化导致容量超负荷，需要心脏保护剂以及旨在稳定水和电解质平衡的一系列措施。人体内水和电解质的含量在整个生命过程中都会发生变化，因此身体对水盐平衡紊乱的反应可能因年龄而异。液体超负荷与危重患者的不良结局呈正相关。现代心脏病学的主要任务之一是寻找衡量不同年龄患者不良因素对心肌影响的方法。我们研究的目的是确定在严重低渗性水合过多的影响下老年实验动物心肌的形态变化，并试图通过米屈肼纠正已确定的变化。材料和方法 本实验按照“欧洲保护用于实验和其他科学目的的脊椎动物公约”（斯特拉斯堡，1986 年）进行。18 只 22 个月大的大鼠分为 3 个系列：2 个实验组和 1 个对照组（每组 6 个）。第一个实验系列的动物通过在 25 天内通过管每天 3 次引入 10 ml 蒸馏水来模拟严重的低渗性水合过多。动物吃煮过的无盐食物，并注射抗利尿激素“Minirin”的合成类似物 (Ferring) 每天 2 次饮水，剂量为 0.01 毫克。此外，在整个实验过程中，第二个实验系列的大鼠每天一次以 50 mg/kg 的剂量腹膜内注射米屈肼。考虑到加压素对心血管系统的潜在影响，对照系列的动物接受正常的饮用水和食物，并且每天两次以0.01mg的剂量注射“Mynyrin”(Ferring)。我们通过公式（RACT+RAV）/ RACMC。结果在给予米屈肼的大鼠心肌中，仅注意到孤立的间质出血，而在第一个实验系列的心肌样本中存在大量出血。左心室的 DCMC 和右心室的 DCMC 分别高于对照，分别为 13.18% (p<0.0001) 和 12.27% (p<0.0001)。RAV 不会改变。左心室 RACT 和右心室 RACT 分别增加 3.72% (p=0.0060) 和 5.23% (p <0.0001)。右心室 RACMC 比控制参数小 0.63% (p = 0.0015)。结论 在老年动物中，米屈肼改善了心肌的血管成分。然而，我们还没有发现药物对其他研究参数的积极影响。左心室 RACT 和右心室 RACT 分别增加 3.72% (p=0.0060) 和 5.23% (p <0.0001)。右心室 RACMC 比控制参数小 0.63% (p = 0.0015)。结论 在老年动物中，米屈肼改善了心肌的血管成分。然而，我们还没有发现药物对其他研究参数的积极影响。左心室 RACT 和右心室 RACT 分别增加 3.72% (p=0.0060) 和 5.23% (p <0.0001)。右心室 RACMC 比控制参数小 0.63% (p = 0.0015)。结论 在老年动物中，米屈肼改善了心肌的血管成分。然而，我们还没有发现药物对其他研究参数的积极影响。