Myocardium Of Wistar Rats Research Articles

Myocardial remodeling in wistar rats with renal dysfunction fed a high-salt diet

BACKGROUND. Dietary adjustment is an important point in the treatment of chronic kidney disease (CKD). However, at present, the effect of a diet with a high NaCl content on the state of the cardiovascular system in patients with early stages of CKD has not been sufficiently studied.The AIM: to evaluate blood pressure levels and changes in the myocardium of Wistar rats with early stage renal dysfunction fed a high-salt diet for a long time.MATERIALS AND METHODS: The study was performed on male Wistar rats. The control group consisted of sham-operated animals (LO-group), receiving a standard diet (0.34 % NaCl), the second – rats subjected to resection of ¾ of the kidney parenchyma, receiving a standard diet (NE-group), the third – rats, subjected to ¾ NE, receiving high sodium diet (4 % NaCl, NE+HSD). After 4 months, the rats were assessed for blood pressure (BP), levels of urea, creatinine, sodium in the blood serum, daily diuresis, albumin content in the urine, myocardial mass index (IMM) and left ventricular myocardial mass index (IMLV), and a histological examination of the myocardium was performed.RESULTS: In rats with kidney dysfunction, an increase in blood pressure was detected, most pronounced in the NE+HSD group. In rats of this group, albumin excretion, connective tissue volume, arterial diameter, thickness of the adventitia and media of myocardial vessels increased relative to the indicators of rats with NE receiving a standard diet. IMLV in NE+HSD rats was higher by 16.4 %, and IMM by 10.9 % than in animals with NE on a standard diet. The groups with NE did not differ from each other in the content of urea and creatinine in the blood serum, although these indicators were higher than in LO animals. There were no differences between groups in serum sodium levels.CONCLUSION: Prolonged consumption of a diet with a high content of table salt contributes to the development of the initial stages of CKD in Wistar rats, promotes blood pressure growth and myocardial remodeling, manifested primarily in the progression of cardiomyocyte hypertrophy and myocardial fibrosis.

Condition of the cardiovascular system in Wistar rats with experimental renal dysfunction

The aim: to evaluate functional and structural changes in blood vessels and myocardium in Wistar rats at different stages of the formation of experimental kidney dysfunction.Materials and Methods. Four groups of animals were studied. The first two groups consisted of rats subjected to 5/6 nephrectomy (NE). The period after NE is 2 or 4 months. The third and fourth groups included sham-operated (SO) animals of a similar observation period. After the end of the experiment, blood pressure was measured in rats, the left ventricular mass index (LVMI) was calculated, a biochemical blood test, histological, immunohistochemical and electron microscopic examination of the myocardium were performed, and the contractile activity of the portal vein was recorded for a period of 2 months (in vitro).Results. 2 months after NE, an increase in blood pressure, LVMI, and a decrease in the autorhythmic contractile activity of the portal vein were detected in rats. At the histological level, thickening of cardiomyocytes and arterial vessel walls and the presence of perivascular fibrosis were noted. After 4 months, in rats with NE, the increase in blood pressure, cardiomyocyte hypertrophy and perivascular fibrosis progressed. The thickness of cardiomyocytes was 14.1±3.11 μm, which was significantly greater than in the group with NE for 2 months (12.5±1.5 μm; p=0.008). At this period of observation, electron microscopic examination revealed deintegration of myofibrils, disruption of myofibril stacking and z-disk structure, and changes in the shape of mitochondria. 2 months after NE, an increase in the area of open capillaries was detected in rats (1902.8±202.9 μm²) compared to the corresponding LO animals (730.4±58.2 μm²; p=0.000). As renal dysfunction develops, the capillary area tends to increase (2139.1±396.5 μm²; p =0.120).Conclusion. In Wistar rats with renal dysfunction, changes were detected not only in the level of blood pressure, but also in the functional activity of the intravenous fluid, as well as in the structural components of the myocardium – cardiomyocytes, stroma and blood vessels. The increase in myocardial mass at the histological level was manifested by a significant increase in the thickness of cardiomyocytes, the volume of connective tissue, and the thickness of the wall of arterial vessels, reaching a maximum value at a longer period after NE.

Myocardial effects of a low-protein diet in experimental kidney dysfunction

THE AIM: to evaluate the effect of low protein diet supplemented with ketosteril on morphological and epigenomic changes in the myocardium of Wistar rats with simulated kidney dysfunction . MATERIALS AND METHODS. The work was performed on male Wistar rats subjected to 5/6 nephrectomy (NE). The first group after NE received a standard diet (20.16% animal protein ), the second – low protein diet (LPD), including 10% ketosteril . Control rats received a standard diet . After 4 months , blood pressure (BP) and left ventricular mass index (LVMI) were assessed in rats , and a histological examination of the myocardium was performed . In the myocardium , the relative expression levels of NF- kB , miRNA-21, miRNA-133, and miRNA-203 were determined . RESULTS. After 4 months in rats with NE on a standard diet , an increase in blood pressure , an increase in the mass index of the LV myocardium was recorded . MBD with the inclusion of 10% Ketosteril slowed down the growth of systolic blood pressure and the development of LV myocardial hypertrophy in rats with kidney dysfunction . At the histological level , the use of LPD provided a decrease in the degree of hypertrophy of cardiomyocytes and degenerative changes in cardiomyocytes . Animals treated with LPD had less pronounced diffuse and perivascular fibrosis compared with animals fed normal food . The use of MBD slowed down the increase in the relative level of expression of the NFκB gene and miRNA-21 in the myocardium of rats with NE and promoted an increase in the expression level of miRNA-133 and miRNA-203 compared to the indices of animals with NE that received standard food . CONCLUSION: long-term use of LPD with the use of ketoanalogues of essential amino acids can have a potential cardioprotective effect in CKD, slowing down the growth of blood pressure , an increase in LV myocardial mass and the formation of structural changes in the myocardium . It is possible that a decrease in the expression of NF- kB and miRNA-21, as well as an increase in the expression of miRNA-203 and 133 in the myocardium , can play a significant role in this .

Ultrastructural Myocardial Reorganization during Experimental Treatment with Doxorubicin and Atorvastatin.

We studied ultrastructural reorganization of the myocardium in Wistar rats treated with doxorubicin (single intraperitoneal injection in a dose of 15 mg/kg) and atorvastatin (daily intragastric administration in a dose of 20 mg/kg for 7 days) individually and in combination. It was found that doxorubicin administered alone or in combination with atorvastatin induces disturbances of varying severity in cardiomyocyte ultrastructure indicating the development of regenerative and plastic myocardial insufficiency. In case of isolated administration of atorvastatin, lytic changes in myofibrils, increased autophagic processes, and segregation of the fibrillar and granular components in the nucleoli appeared in the ultrastructure of some cardiomyocytes with increasing the observation period. Ultrastructural stereological analysis revealed a tendency to a decrease in the volume density of myofibrils and mitochondria in all experimental groups in comparison with the control.

Magnetic Resonance Imaging in Assessment of Cardiac Remodeling in Rats with Experimental Arterial Hypertension.

Magnetic resonance imaging was employed to examine the morphofunctional status of myocardium in Wistar rats with multifactor cardiovasorenal model of arterial hypertension. In 3 months after the onset of experiment, the rats demonstrated a pronounced hypertrophy in left ventricular myocardium mostly due to thickening of the posterior and lateral walls against the background of relatively stable thickness of ventricular septum. The left ventricular endsystolic volume markedly increased in parallel with moderate increase of the end-diastolic volume. The standard calculated indices were used for precise assessment of the type of remodeling of individual myocardial structures. The study showed that multifactor arterial hypertension model was characterized by domination of hypertrophic mode of the left ventricular remodeling, whereas the concentric variant was observed more rarely by 2.5 times. The greatest alterations were observed in the posterior and lateral walls of the left ventricle, which could result from the hemodynamic effects of hypervolemic arterial hypertension.

IMMUNOHISTOCHEMICAL EVALUATION OF VASOENDOTHELIAL GROWTH FACTOR RECEPTOR-2 (VEGFR2) EXPRESSION IN RAT CARDIOMYOCYTES UNDER DOXORUBICIN AND BETULONIC ACID AMIDE ADMINISTRATION

The aim of the study is to perform an immunohistochemical analysis of the expression of the vascular endothelial growth factor receptor 2 (VEGFR2) in the myocardium of Wistar rats in doxorubicin-induced cardiomyopathy and the administration of betulonic acid amide as an agent with a polytarget effect in comparison with the severity of destructive processes in heart muscle cells. Material and methods. Wistar male rats (total 51 animals) were used in the work with isolated and combined administration of a single sublethal dose of doxorubicin (7 mg/kg) and course administration of betulonic acid amide at doses of 50 mg/kg/day and 100 mg/kg/day for 3 and 14 days. Immunohistochemical evaluation of VEGFR2 expression in the myocardium was carried out with the calculation of the index of VEGFR2-positive cardiomyocytes; the volume density of cardiomyocytes with lytic changes was estimated using stereological analysis. Results and discussion. A single administration of doxorubicin (at a dose of 7 mg/kg) caused destructive changes in cardiomyocytes and hemodynamic disorders in myocardium, which increased with the duration of the experiment (14 days). The complex of the revealed structural and metabolic lesions reflected the development of regenerative-plastic insufficiency of cardiomyocytes, which is the basis of cardiac insufficiency in anthracycline cardiomyopathy. Morphological changes in the myocardium with isolated administration of betulonic acid amide were largely determined by the dose used. At a dose of 100 mg/kg, myocardial changes were similar in severity with doxorubicin-induced changes. Combined use of doxorubicin and betulonic acid amide revealed the most significant structural damage of the myocardium. It was shown that the increase in the volume density of lytic altered cardiomyocytes correlated with a significant increase in VEGFR2 expression (correlation coefficient varied from 0.620 to 0.980).

Effects of testosterone enanthate and resistance training on myocardium in Wistar rats; clinical and anatomical pathology.

This study was performed to determine the effects of 8weeks testosterone enanthate (TE) injection and resistance training (RT) on cardiac muscle in male Wistar rats. A total of 28 male adult Wistar rats were randomly divided into 4 groups; control+placebo, RT+placebo, TE and TE+RT. Testosterone enanthate (20mg/kg BW, IM) and placebo (olive oil; 0.2ml, IM) were injected twice a week for 2months. The RT consisted of climbing (5 reps/3 sets) a ladder carrying a load suspended from the tail. The serum activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) and creatine kinase MB (CK-MB) and serum level of creatinine, urea and cardiac troponin I (CTnI) were evaluated. After sacrifice, samples from myocardial muscle were collected for histopathology evaluation. The serum concentration of CTnI and CK-MB activity significantly increased in group RT compared with control (p<.05). In group RT+TE, all biomarkers of muscle damage (CTnI, CK-MB, AST, LDH) were significantly more than those in control (p<.05). Also, mild myocardial hypertrophy was observed in RT and RT+TE groups. The higher level of all heart damage biomarkers in the RT+TE group rather than control may indicate the synergistic effects of medication and exercise.

EFFECT OF EPINEPHRINE ADMINISTRATION ON MYOCARDIAL REMODELING IN EXPERIMENTAL STUDY

Aim. To study structural changes in the myocardium of Wistar rats after a single administration of epinephrine. Material and methods . Structural changes in male Wistar rat’s left (LV) and right (RV) ventricle myocardium after a single injection of epinephrine were studied. Results. The density of extracellular spaces in bothLV and RV myocardium increases first after single epinephrine injection (after 2 hours), and then-decreases below reference values in the next control points. It remains so even after 1 month after a single injection of epinephrine in both theLV (3.95±0.64-vs 6.83±0.30 vol% in the control group; p<0.05) and RV (4.71±0.55 vs 6.09±0.33 vol% in the control group; p<0.05). The density of collagen-fibers in both ventricles increases in all the control points, and more significantly in the RV than in theLV after 2 and 24 hours. After 2 hours the density-of collagen fibers in the RV was 25.8±1.39 vs 19.85±1.50 vol% in theLV (p<0.05), and after 24 hours it is 1.5 times higher – 30.47±1.98 vs-18.47±1.27 vol%, respectively, (p<0.05). The cardiomyocytes density in both ventricles decreases considerably without reaching control values even-in 1 month after a single injection of epinephrine. Conclusion. Severe structural changes develop after single administration of epinephrine in both ventricles rat’s myocardium within 2 hours and persist during the first day. At that structural remodeling of theLV and RV ventricles is asynchronous. Complete regression of morphological changes in the myocardium bothLV and RV does not occur even after 1 month after a single injection of epinephrine. The high values of collagen fibers density, that are observed in both ventricles in acute adrenergic stress model, make it possible to assume that single administration of epinephrine triggers myocardial fibrogenesis mechanisms, which are continuing despite the cessation of drug exposure.

Remodeling of myocardium in rat with chronic dyslipidemia and under conditions of verapamil treatment.

The type and intensity of remodeling (structural reorganization) of the myocardium in Wistar rats were studied under conditions of experimental chronic dyslipidemia and verapamil treatment. Long (64 days) atherogenic diet caused dyslipidemia and led to reduction of the heart percent weight. The cytopathic effect of dyslipidemia manifested in more intense lytic injuries of cardiomyocytes, development of diffuse and small focal cardiosclerosis under conditions of manifest circulatory disorders. Remodeling of the myocardium during various periods of the experiment manifested in a higher connective tissue/cardiomyocyte volume ratio (by 74% after 30 days and by 58-62% after 64 days of experiment). Verapamil injection promoted attenuation of lytic changes in cardiomyocytes and in fibroplastic reactions of the stroma, but failed to prevent them completely.

DOPAMINE EFFECT ON CARDIAC REMODELING IN EXPERIMENT

Aim. To study morphologic changes in myocardium of Wistar rats caused by single and long term dopamine administration. Methods. In acute study dopamine 10 mkg/kg was administrated to 15 rats by a single intraperitoneal injection. The material was taken in 2, 6, 24 hours and in 1 month after drug administration. In chronic study dopamine 10 mkg/kg was administrated to 15 rats 3 times a day by intraperitoneal injections during 2 weeks. The material was taken just after the drug administration was stopped and in 1 month of animals keeping without stress and drug influences. Control group included 15 rats comparable with experimental animals in age and weight. They were keeped without stress and drug influences. Morphometric parameters of left and right ventricles were evaluated as well as density of cardiomyocytes, collagen, vessels and volume of extracellular space. Results. The enlargement of cardiac fibrosis is found both in acute, and in chronic study. In acute study cardiac fibrosis was located mainly in a right ventricle. In chronic study cardiac fibrosis was located in both ventricles, but also mainly in a right one. Conclusion. Significant morphological «asynchronism» of the left and right ventricles remodeling requires elaboration of methods of myocardium protection and cardiac function control during dopamine administration.

Effect of spironolactone on hypertrophy of left ventricular myocardium in Wistar rats with experimental uremia

Chronic renal failure was modeled in rats by partial nephrectomy. Blood pressure, heart rate, concentrations of aldosterone, urea, creatinine, electrolytes, and protein, index of hypertrophy of visceral organs, and 24-h diuresis were evaluated. In rats treated with spironolactone, the index of myocardial hypertrophy did not considerably differ from that in sham-operated animals, whereas in untreated rats the test parameters considerably differ from the control. We concluded that the blockade of aldosterone receptors with spironolactone produced a cardioprotective effect in Wistar rats with subtotal nephrectomy.

PPARγ agonist induced cardiac enlargement is associated with reduced fatty acid and increased glucose utilization in myocardium of Wistar rats

In toxicological studies, high doses of peroxisome proliferator-activated receptor-gamma (PPARγ) agonists cause cardiac enlargement. To investigate whether this could be explained by a large shift from free fatty acid to glucose utilization by the heart, Wistar rats were treated for 2–3 weeks with a potent, selective PPARγ agonist (X334, 3 μmol/kg/d), or vehicle. X334 treatment increased body-weight gain and ventricular mass. Treatment lowered plasma triglycerides by 61%, free fatty acid levels by 72%, insulin levels by 45%, and reduced total plasma protein concentration by 7% (indicating plasma volume expansion) compared to vehicle animals. Fasting plasma glucose levels were unaltered. To assess cardiac free fatty acid and glucose utilization in vivo we used simultaneous infusions of non-β-oxidizable free fatty acid analogue, [9,10- 3H]( R)-2-bromopalmitate and [U- 14C]2-deoxy- d-glucose tracers, which yield indices of local free fatty acid and glucose utilization. In anesthetized, 7 h fasted animals, left ventricular glucose utilization was increased to 182% while free fatty acid utilization was reduced by 28% ( P < 0.05) compared to vehicle. In separate studies we attempted to prevent the X334-induced hypolipidemia. Various dietary fat supplements were unsuccessful. By contrast, restricting the time during which the treated animals had access to food (promoting endogenous lipolysis), restored plasma free fatty acid from 27% to 72% of vehicle control levels and prevented the cardiac enlargement. Body-weight gain in these treated-food restricted rats was not different from vehicle controls. In conclusion, the cardiac enlargement caused by intense PPARγ activation in normal animals is associated with marked changes in free fatty acid/glucose utilization and the enlargement can be prevented by restoring free fatty acid availability.

Morphological characteristics of myocardial remodeling during compensatory hypertrophy in aging Wistar rats.

Remodeling of the myocardium in Wistar rats during aging is characterized by cardiomyocyte hypertrophy and increase of their total volume in the left ventricle; the total volume of the connective tissue also increases without marked changes in cardiomyocyte count and total volume of blood capillaries. The number of cardiomyocytes with contracture injuries of different severity in the myocardium of aging animals increases against the background of hemodynamic disorders. At the cellular level, compensatory hypertrophy of cardiomyocytes during aging is characterized by a pronounced increase in the myofibril bulk paralleled by relative deficiency of the mitochondria and pronounced deficiency of agranular sarcoplasmic reticulum and T system, involved in the regulation of intracellular Ca2+.

Peculiarities of intracellular regeneration of cardiomyocytes during plastic myocardial insufficiency.

We performed morphological assay of the myocardium in Wistar rats with anthracycline cardiomyopathy and SHR rats with genetically determined arterial hypertension causing hypertrophic cardiomyopathy. Both disorders were accompanied by a decrease in protein synthesis and development of plastic cardiomyocyte insufficiency. Electron microscopy revealed peculiarities of intracellular regeneration of cardiomyocytes. We observed disorientation of newly formed myofibrils lying between preserved myofibrils. These myofibrils were positioned perpendicular or at angle to the long axis of muscle fibers, or extended from the Z line (in a fan-like manner) crossing each other. Regeneration disturbances also included excessive elongation of myofibrils. These abnormalities of myofibril regeneration were related to changes in transcription and translation in cardiomyocytes, due to DNA damages caused by cardiotoxic doses of rubomycin.

Role of heat shock proteins in the formation of stress resistance in different animal strains

In response to heat shock five isoforms of hsp 70 are accumulated in the myocardium of Wistar rats highly resistant to stress in comparison with only 3 isoforms of hsp 70 in August rats with a lower resistance to stress. This suggests that genetic mechanisms which determine the stress resistance of a particular strain are probably related to transcription of hsp 70 genes.

Ultrastructural mechanisms of myocardial atrophy in albino rats during starvation

By means of complex morphological, morphometrical and stereological analyses the myocardium of Wistar rats was studied in full alimentary starvation during 6 days. The availability of two mechanisms of myocardial atrophy in adaptation to full starvation was revealed, these are the diminution of dimensions of parenchymatous elements and the decrease of muscle cell number. By ultrastructural investigation of cardiomyocytes the signs of structural protein synthesis decline were revealed, this is a simple myocardial atrophy. In quantitative analysis of cardiomyocytes the decrease of their number without changes in proportions of cells with different nuclei number was observed, that indicated systematic character of muscle cell elimination out of myocardium by apoptosis mechanism involvement, this is a numerical myocardial atrophy. Stereological analysis of myocardial atrophy development in conditions of full starvation determined the main regulated indices, these are the absolute total myofibril mass and mitochondrial mass and surface area.

Tissue stereologic analysis of myocardial atrophy during hypokinesia

The myocardium of Wistar rats which were in a state of hypokinesia for 5, 15 and 30 days was assayed morphologically. Morphometric and stereological methods were used to measure the diameter of cardiomyocytes, the volume and surface densities of muscle fibers and interstitial connective tissue. Myocardial atrophy (absolute heart weight loss, reduction in the cardiomyocyte diameter) was shown to develop in the course of hypokinesia. Informational analysis revealed the increased enthropy and relative enthropy as well as reduction of excess myocardial tissue. Long-term immobilization also resulted in an increase of the relative volume density of the stroma, collagenization of the interstitial connective tissue, and marked tendency toward diminution of the surface-volume ratio of the capillaries.