Local renin-angiotensin system regulates left ventricular hypertrophy induced by swimming training independent of circulating renin: a pharmacological study

Angiotensin II Promotes Skeletal Muscle Angiogenesis Induced by Volume-Dependent Aerobic Exercise Training: Effects on miRNAs-27a/b and Oxidant-Antioxidant Balance

Aerobic exercise training (ET) produces beneficial adaptations in skeletal muscles, including angiogenesis. The renin–angiotensin system (RAS) is highly involved in angiogenesis stimuli. However, the molecular mechanisms underlying capillary growth in skeletal muscle induced by aerobic ET are not completely understood. This study aimed to investigate the effects of volume-dependent aerobic ET on skeletal muscle angiogenesis involving the expression of miRNAs-27a and 27b on RAS and oxidant–antioxidant balance. Eight-week-old female Wistar rats were divided into three groups: sedentary control (SC), trained protocol 1 (P1), and trained protocol 2 (P2). P1 consisted of 60 min/day of swimming, 5×/week, for 10 weeks. P2 consisted of the same protocol as P1 until the 8th week, but in the 9th week, rats trained 2×/day, and in the 10th week, trained 3×/day. Angiogenesis and molecular analyses were performed in soleus muscle samples. Furthermore, to establish ET-induced angiogenesis through RAS, animals were treated with an AT1 receptor blocker (losartan). Aerobic ET promoted higher VO₂ peak and exercise tolerance values. In contrast, miRNA-27a and -27b levels were reduced in both trained groups, compared with the SC group. This was in parallel with an increase in the ACE1/Ang II/VEGF axis, which led to a higher capillary-to-fiber ratio. Moreover, aerobic ET induced an antioxidant profile increasing skeletal muscle SOD2 and catalase gene expression, which was accompanied by high nitrite levels and reduced nitrotyrosine concentrations in the circulation. Additionally, losartan treatment partially re-established the miRNAs expression and the capillary-to-fiber ratio in the trained groups. In summary, aerobic ET promoted angiogenesis through the miRNA-27a/b–ACE1/Ang II/VEGF axis and improved the redox balance. Losartan treatment demonstrates the participation of RAS in ET-induced vascular growth. miRNAs and RAS components are promising potential targets to modulate angiogenesis for combating vascular diseases, as well as potential biomarkers to monitor training interventions and physical performance.

High-volume endurance exercise training stimulates hematopoiesis by increasing ACE NH2-terminal activity

One of the health benefits of endurance exercise training (ET) is the stimulation of hematopoiesis. However, the mechanisms underlying ET-induced hematopoietic adaptations are understudied. N-Acetyl-Seryl-Aspartyl-Lysyl-Proline (Ac-SDKP) inhibits proliferation of early hematopoietic progenitor cells. The angiotensin I-converting enzyme (ACE) NH2-terminal promotes hematopoiesis by inhibiting the anti-hematopoietic effect of Ac-SDKP. Here we demonstrate for the first time the role of ACE NH2-terminal in ET-induced hematopoietic adaptations. Wistar rats were subjected to 10 weeks of moderate-(T1) and high-(T2) volume swimming-training. Although both protocols induced classical ET-associated adaptations, only T2 increased plasma ACE NH2-domain activity (by 40%, P=0.0003) and reduced Ac-SDKP levels (by 50%, P<0.0001). T2 increased the number of hematopoietic stem cells (HSCs; ∼200%, P=0.0008), early erythroid progenitor colonies (∼300%, P<0.0001) and reticulocytes (∼500%, P=0.0007), and reduced erythrocyte lifespan (∼50%, P=0.022). Following, Wistar rats were subjected to T2 or T2 combined with ACE NH2-terminal inhibition (captopril (Cap) treatment: 10 mg.kg-1.day-1). T2 combined with ACE NH2-terminal inhibition prevented Ac-SDKP decrease and attenuated ET-induced hematopoietic adaptations. Altogether, our findings show that ET-induced hematopoiesis was at least partially associated with increased ACE NH2-terminal activity and reduction in the hematopoietic inhibitor Ac-SDKP.

Downregulation of miR-26b-5p, miR-204-5p, and miR-497-3p Expression Facilitates Exercise-Induced Physiological Cardiac Hypertrophy by Augmenting Autophagy in Rats

Exercise-induced autophagy is associated with physiological left ventricular hypertrophy (LVH), and a growing body of evidence suggests that microRNAs (miRNAs) can regulate autophagy-related genes. However, the precise role of miRNAs in exercise induced autophagy in physiological LVH has not been fully defined. In this study, we investigated the microRNA–autophagy axis in physiological LVH and deciphered the underlying mechanism using a rat swimming exercise model. Rats were assigned to sedentary control (CON) and swimming exercise (EX) groups; those in the latter group completed a 10-week swimming exercise without any load. For in vitro studies, H9C2 cardiomyocyte cell line was stimulated with IGF-1 for hypertrophy. We found a significant increase in autophagy activity in the hearts of rats with exercise-induced physiological hypertrophy, and miRNAs showed a high score in the pathway enriched in autophagy. Moreover, the expression levels of miR-26b-5p, miR-204-5p, and miR-497-3p showed an obvious increase in rat hearts. Adenovirus-mediated overexpression of miR-26b-5p, miR-204-5p, and miR-497-3p markedly attenuated IGF-1-induced hypertrophy in H9C2 cells by suppressing autophagy. Furthermore, miR-26b-5p, miR-204-5p, and miR-497-3p attenuated autophagy in H9C2 cells through targeting ULK1, LC3B, and Beclin 1, respectively. Taken together, our results demonstrate that swimming exercise induced physiological LVH, at least in part, by modulating the microRNA–autophagy axis, and that miR-26b-5p, miR-204-5p, and miR-497-3p may help distinguish physiological and pathological LVH.

Alteration in cardiac PI3K/Akt/mTOR and ERK signaling pathways with the use of growth hormone and swimming, and the roles of miR21 and miR133

Athletes misuse recombinant human growth hormone (r-hGH) to enhance their performance. Although r-hGH is known to increase cardiac hypertrophy, the underlying molecular mechanism remains unclear. The aim of the present study was to investigate the role of r-hGH in cardiac intracellular signaling pathways and of miR-21 and miR-133 expression in rat hearts during exercise. A total of 36 adult male Sprague-Dawley rats were divided into sedentary control (SC, n=9), swimming exercise (SE, n=8), r-hGH (GH, n=10) and swimming exercise plus r-hGH (SE-GH, n=9) groups. The exercise groups completed a 1-h swimming exercise 5 times a week for 8 weeks. Subcutaneous r-hGH was administered as 0.3 mg/kg/day. Phosphoinositide-3-kinase (PI3K), serine/threonine protein kinase 1 (AKT1), extracellular signal-regulated kinase (ERK), microRNA (miR)-21 and miR-133 expression was evaluated in ventricular muscle by real-time quantitative polymerase chain reaction. Protein expression of PI3K, AKT1, ERK and mechanistic target of rapamycin (mTOR) was also assessed by immunohistochemistry. Statistical differences were analyzed by two-way ANOVA. PI3K and AKT1 expression and the gene and protein levels was notably increased in the SE-GH group compared with in SC ventricular tissues (P<0.05). mTOR protein expression was higher in the GH, SE and SE-GH groups compared with in the SC group (P<0.05, <0.05 and <0.001, respectively). ERK gene/protein expression was similar across all groups. miR-21 and miR-133 levels in ventricular muscle were higher in the SE and GH groups than those in the SC group. In summary, growth hormone application coupled with swimming exercise appeared to affect the PI3K/AKT/mTOR signaling pathway in the left ventricular tissue of rats; however, ERK signaling pathway appeared inactive in physiological left ventricular hypertrophy caused by swimming and GH administration over 8 weeks. Furthermore, GH treatment resulted in increased miR-21 and miR-133 expression. Future study by our group will aim to assess the effects of higher dose GH treatment.

Cardiac AT(1) receptor-dependent and IGF1 receptor-independent signaling is activated by a single bout of resistance exercise

AT(1) receptor (AT1R) blockade prevents physiological cardiac hypertrophy induced by resistance training. Also, our group showed that a single bout of resistance exercise (RE) activates the AKT/mTOR which was also inhibited by AT1R blocker. Here, we investigated whether IGF1-receptor (IGF1-R) and MAPKs were also activated after a single bout of RE. Wistar rats were divided into Sedentary (Sed), Sedentary treated with losartan (Sed+LOS), Exercise (EX), and Exercise treated with losartan (EX+LOS). Cardiac tissue was obtained 5 and 30 min after 4 sets of 12 repetitions of squat exercise (80 % 1RM). We demonstrated that a single bout of RE did not induce IGF1-R tyrosine phosphorylation. ERK1/2 and P38 phosphorylation levels were elevated in the EX 5min and EX 30min groups however, only ERK1/2 was inhibited by losartan treatment (AT1R blocker). Next, we showed that beta-arrestin-2 expression increased 28 % in trained animals compared to sedentary group. Altogether, our results demonstrate that AT1R, but not IGF1-R, may exert the hypertrophic cardiac stimulus RE-induced. Also, activation of AKT/mTOR and ERK1/2 pathways may occur through the beta-arrestin-dependent pathway.

The Effects of Nandrolone Decanoate Along with Prolonged Low-Intensity Exercise on Susceptibility to Ventricular Arrhythmias

We examined the influence of chronic administration of nandrolone decanoate with low-intensity endurance swimming exercise on susceptibility to lethal ventricular arrhythmias in rat. The animal groups included the control group, exercise group (EX), nandrolone group (Nan), vehicle group (Arach), trained vehicle group (Arach + Ex) and trained nandrolone group (Nan + Ex) that treated for 8 weeks. Then, arrhythmia induction was performed by intravenous infusion of aconitine and electrocardiogram recorded. Then, malondialdehyde (MDA), hydroxyproline (HYP) and glutathione peroxidase of heart tissue were measured. Chronic administration of nandrolone with low-intensity endurance swimming exercise had no significant effect on blood pressure, heart rate and basal ECG parameters except RR interval that showed increase (P < 0.05). Low-intensity exercise could prevent the incremental effect of nandrolone on MDA and HYP significantly. It also increased the heart hypertrophy index (P < 0.05) and reduced the abating effect of nandrolone on animal weighting. Nandrolone along with exercise significantly increased the duration of VF (P < 0.05) and reduced the VF latency (P < 0.05). The findings suggest that chronic co-administration of nandrolone with low-intensity endurance swimming exercise to some extent facilitates the occurrence of ventricular fibrillation in rat. Complementary studies are needed to elucidate the involved mechanisms of this abnormality.

Direct renin inhibitor therapy and swimming training: hemodynamic and cardiac effects in hypertensive and normotensive rats

PURPOSE

This study aimed to analyze the hemodynamic and cardiac effects of direct renin inhibitor (DRI) treatment and swimming training in hypertensive rats.

METHODS

Seventy-seven rats were divide into eight groups: sedentary normotensive (SN), trained normotensive (TN), sedentary normotensive treated with DRI (SN_DRI), trained normotensive treated with DRI (TN_DRI), sedentary hypertensive (SH), trained hypertensive (TH), sedentary hypertensive treated with DRI (SH_DRI), trained hypertensive treated with DRI (TH_DRI). Swimming training occurred for up to 60 min, five times a week for four weeks. The hypertensive animals were treated with 20 mg ċ kg(-1) ċ day(-1) L-NAME for four weeks. Groups treated with DRI received 10 mg ċ kg(-1) ċ day(-1) of aliskiren for four weeks. After the treatment period, all the animals underwent femoral artery catheterization surgery for direct measurement of cardiovascular variables.

RESULTS

The SH group presented hypertension (136.4 ± 5.0 mmHg) compared to the SN (107.1 ± 1.7 mmHg). The TH group showed lower mean arterial pressure (MAP) than the SH (121.1 ± 1.3 mmHg), but the treatment with DRI did not attenuate hypertension (128.2 ± 4.9 mmHg). The analysis of collagen areas demonstrated that treatment with DRI may attenuate cardiac remodeling in situations of hypertension, in the condition of treatment alone or combined with physical training.

CONCLUSION

Both interventions in combination may be more effective at reducing cardiovascular risk in hypertensive subjects.

Exercise training in hypertension: Role of microRNAs

Hypertension is a complex disease that constitutes an important public health problem and demands many studies in order to understand the molecular mechanisms involving his pathophysiology. Therefore, an increasing number of studies have been conducted and new therapies are continually being discovered. In this context, exercise training has emerged as an important non-pharmacological therapy to treat hypertensive patients, minimizing the side effects of pharmacological therapies and frequently contributing to allow pharmacotherapy to be suspended. Several mechanisms have been associated with the pathogenesis of hypertension, such as hyperactivity of the sympathetic nervous system and renin-angiotensin aldosterone system, impaired endothelial nitric oxide production, increased oxygen-reactive species, vascular thickening and stiffening, cardiac hypertrophy, impaired angiogenesis, and sometimes genetic predisposition. With the advent of microRNAs (miRNAs), new insights have been added to the perspectives for the treatment of this disease, and exercise training has been shown to be able to modulate the miRNAs associated with it. Elucidation of the relationship between exercise training and miRNAs in the pathogenesis of hypertension is fundamental in order to understand how exercise modulates the cardiovascular system at genetic level. This can be promising even for the development of new drugs. This article is a review of how exercise training acts on hypertension by means of specific miRNAs in the heart, vascular system, and skeletal muscle.

An analysis of the global expression of microRNAs in an experimental model of physiological left ventricular hypertrophy

Background

MicroRNAs (miRs) are a class of small non-coding RNAs that regulate gene expression. Studies of transgenic mouse models have indicated that deregulation of a single miR can induce pathological cardiac hypertrophy and cardiac failure. The roles of miRs in the genesis of physiological left ventricular hypertrophy (LVH), however, are not well understood.

Objective

To evaluate the global miR expression in an experimental model of exercise-induced LVH.

Methods

Male Balb/c mice were divided into sedentary (SED) and exercise (EXE) groups. Voluntary exercise was performed on an odometer-monitored metal wheels for 35 days. Various tests were performed after 7 and 35 days of training, including a transthoracic echocardiography, a maximal exercise test, a miR microarray (miRBase v.16) and qRT-PCR analysis.

Results

The ratio between the left ventricular weight and body weight was increased by 7% in the EXE group at day 7 (p<0.01) and by 11% at day 35 of training (p<0.001). After 7 days of training, the microarray identified 35 miRs that were differentially expressed between the two groups: 20 were up-regulated and 15 were down-regulated in the EXE group compared with the SED group (p = 0.01). At day 35 of training, 25 miRs were differentially expressed: 15 were up-regulated and 10 were decreased in the EXE animals compared with the SED animals (p<0.01). The qRT-PCR analysis demonstrated an increase in miR-150 levels after 35 days and a decrease in miR-26b, miR-27a and miR-143 after 7 days of voluntary exercise.

Conclusions

We have identified new miRs that can modulate physiological cardiac hypertrophy, particularly miR-26b, -150, -27a and -143. Our data also indicate that previously established regulatory gene pathways involved in pathological LVH are not changed in physiological LVH.

Swimming training prevents fat deposition and decreases angiotensin II-induced coronary vasoconstriction in ovariectomized rats

We investigated the effects of chronic swimming training (ST) on the deposition of abdominal fat and vasoconstriction in response to angiotensin II (ANG II) in the coronary arterial bed of estrogen deficient rats. Twenty-eight 3-month old Wistar female rats were divided into 4 groups: sedentary sham (SS), sedentary-ovariectomized (SO), swimming-trained sham (STS) and swimming-trained ovariectomized (STO). ST protocol consisted of a continuous 60-min session, with a 5% BW load attached to the tail, completed 5 days/week for 8-weeks. The retroperitoneal, parametrial, perirenal and inguinal fat pads were measured. The intrinsic heart rate (IHR), coronary perfusion pressure (CPP) and a concentration-response curve to ANG II in the coronary bed was constructed using the Langendorff preparation. Ovariectomy (OVX) significantly reduced 17-β-estradiol plasma levels in SO and STO groups (p<0.05). The STO group had a significantly reduced retroperitoneal and parametrial fat pad compared with the SO group (p<0.05). IHR values were similar in all groups; however, baseline CPP was significantly reduced in the SO, STS and STO groups compared with the SS group (p<0.05). ANG II caused vasoconstriction in the coronary bed in a concentration-dependent manner. The SO group had an increased response to ANG II when compared with all other experimental groups (p<0.05), which was prevented by 8-weeks of ST in the STO group (p<0.05). OVX increased ANG II-induced vasoconstriction in the coronary vascular bed and abdominal fat pad deposition. Eight weeks of swimming training improved these vasoconstrictor effects and decreased abdominal fat deposition in ovariectomized rats.

Activation of renin-angiotensin system is involved in dyslipidemia-mediated renal injuries in apolipoprotein E knockout mice and HK-2 cells

Background

Dyslipidemia and activation of renin-angiotensin system (RAS) contribute to the progression of chronic kidney disease (CKD). This study investigated possible synergistic effects of intrarenal RAS activation with hyperlipidemia in renal injuries.

Methods

Apolipoprotein knockout mice were fed with normal chow diet (control) or high fat diet (HF group) for eight weeks. Human proximal tubular epithelial cell line (HK-2) was treated without (control) or with cholesterol (30 μg/ml) plus 25-hydroxycholesterol (1 μg/ml) (lipid group) for 24 hours. The plasma lipid profile and RAS components were determined by clinical biochemistry assay and radiommunoassay, respectively. Collagen deposition in kidneys was evaluated by Masson-staining. The gene and protein expressions of molecules involved in RAS components and biomarkers of epithelial mesenchymal transition (EMT) were examined by real-time PCR, immunochemical staining, and Western blot.

Results

The mice fed with high-fat diet showed significant hyperlipidemia with collagen deposition in renal tubular interstitium compared to controls. The plasma levels of renin, angiotensin I, and angiotensin II were no difference in two groups. However, the kidneys of HF group showed up-regulated RAS components, which were positively associated with increased plasma levels of triglyceride, total cholesterol, and LDL. These effects were further confirmed by in vitro studies. Lipid loading induced HK-2 cells underwent EMT, which was closely associated with the increased expressions of intracellular RAS components.

Conclusions

Local RAS activation was involved in hyperlipidemia-mediated renal injuries, suggesting that there are synergistic effects resulting from RAS activation with hyperlipidemia that accelerates the progression of CKD.

Anabolic steroid associated to physical training induces deleterious cardiac effects

PURPOSE

Cardiac aldosterone might be involved in the deleterious effects of nandrolone decanoate (ND) on the heart. Therefore, we investigated the involvement of cardiac aldosterone, by the pharmacological block of AT1 or mineralocorticoid receptors, on cardiac hypertrophy and fibrosis.

METHODS

Male Wistar rats were randomized into eight groups (n = 14 per group): Control (C), nandrolone decanoate (ND), trained (T), trained ND (TND), ND + losartan (ND + L), trained ND + losartan (TND + L), ND + spironolactone (ND + S), and trained ND + spironolactone (TND + S). ND (10 mg·kg(-1)·wk(-1)) was administered during 10 wk of swimming training (five times per week). Losartan (20 mg·kg(-1)·d(-1)) and spironolactone (10 mg·kg(-1)·d(-1)) were administered in drinking water.

RESULTS

Cardiac hypertrophy was increased 10% by using ND and 17% by ND plus training (P < 0.05). In both groups, there was an increase in the collagen volumetric fraction (CVF) and cardiac collagen type III expression (P < 0.05). The ND treatment increased left ventricle-angiotensin-converting enzyme I activity, AT1 receptor expression, aldosterone synthase (CYP11B2), and 11-β hydroxysteroid dehydrogenase 2 (11β-HSD2) gene expression and inflammatory markers, TGFβ and osteopontin. Both losartan and spironolactone inhibited the increase of CVF and collagen type III. In addition, both treatments inhibited the increase in left ventricle-angiotensin-converting enzyme I activity, CYP11B2, 11β-HSD2, TGFβ, and osteopontin induced by the ND treatment.

CONCLUSIONS

We believe this is the first study to show the effects of ND on cardiac aldosterone. Our results suggest that these effects may be associated to TGFβ and osteopontin. Thus, we conclude that the cardiac aldosterone has an important role on the deleterious effects on the heart induced by ND.

Lessons from in vitro studies and a related intracellular angiotensin II transgenic mouse model

In the classical renin-angiotensin system, circulating ANG II mediates growth stimulatory and hemodynamic effects through the plasma membrane ANG II type I receptor, AT1. ANG II also exists in the intracellular space in some native cells, and tissues and can be upregulated in diseases, including hypertension and diabetes. Moreover, intracellular AT1 receptors can be found associated with endosomes, nuclei, and mitochondria. Intracellular ANG II can function in a canonical fashion through the native receptor and also in a noncanonical fashion through interaction with alternative proteins. Likewise, the receptor and proteolytic fragments of the receptor can function independently of ANG II. Participation of the receptor and ligand in alternative intracellular pathways may serve to amplify events that are initiated at the plasma membrane. We review historical and current literature relevant to ANG II, compared with other intracrines, in tissue culture and transgenic models. In particular, we describe a new transgenic mouse model, which demonstrates that intracellular ANG II is linked to high blood pressure. Appreciation of the diverse, pleiotropic intracellular effects of components of the renin-angiotensin system should lead to alternative disease treatment targets and new therapies.

Aerobic exercise training-induced left ventricular hypertrophy involves regulatory MicroRNAs, decreased angiotensin-converting enzyme-angiotensin ii, and synergistic regulation of angiotensin-converting enzyme 2-angiotensin (1-7)

Aerobic exercise training leads to a physiological, nonpathological left ventricular hypertrophy; however, the underlying biochemical and molecular mechanisms of physiological left ventricular hypertrophy are unknown. The role of microRNAs regulating the classic and the novel cardiac renin-angiotensin (Ang) system was studied in trained rats assigned to 3 groups: (1) sedentary; (2) swimming trained with protocol 1 (T1, moderate-volume training); and (3) protocol 2 (T2, high-volume training). Cardiac Ang I levels, Ang-converting enzyme (ACE) activity, and protein expression, as well as Ang II levels, were lower in T1 and T2; however, Ang II type 1 receptor mRNA levels (69% in T1 and 99% in T2) and protein expression (240% in T1 and 300% in T2) increased after training. Ang II type 2 receptor mRNA levels (220%) and protein expression (332%) were shown to be increased in T2. In addition, T1 and T2 were shown to increase ACE2 activity and protein expression and Ang (1-7) levels in the heart. Exercise increased microRNA-27a and 27b, targeting ACE and decreasing microRNA-143 targeting ACE2 in the heart. Left ventricular hypertrophy induced by aerobic training involves microRNA regulation and an increase in cardiac Ang II type 1 receptor without the participation of Ang II. Parallel to this, an increase in ACE2, Ang (1-7), and Ang II type 2 receptor in the heart by exercise suggests that this nonclassic cardiac renin-angiotensin system counteracts the classic cardiac renin-angiotensin system. These findings are consistent with a model in which exercise may induce left ventricular hypertrophy, at least in part, altering the expression of specific microRNAs targeting renin-angiotensin system genes. Together these effects might provide the additional aerobic capacity required by the exercised heart.

MicroRNAs 29 are involved in the improvement of ventricular compliance promoted by aerobic exercise training in rats

MiRNAs regulate cardiac development, hypertrophy, and angiogenesis, but their role in cardiac hypertrophy (CH) induced by aerobic training has not previously been studied. Aerobic training promotes physiological CH preserving cardiac function. This study assessed involvement of miRNAs-29 in CH of trained rats. Female Wistar rats (n=7/group) were randomized into three groups: sedentary (S), training 1 (T1), training 2 (T2). T1: swimming sessions of 60 min/5 days/wk/10 wk. T2: similar to T1 until 8th wk. On the 9th wk rats swam 2×/day, and on the 10th wk 3×/day. MiRNAs analysis was performed by miRNA microarray and confirmed by real-time PCR. We assessed: markers of training, CH by ratio of left ventricle (LV) weight/body wt and cardiomyocytes diameter, pathological markers of CH (ANF, skeletal α-actin, α/β-MHC), collagen I and III (COLIAI and COLIIIAI) by real-time PCR, protein collagen by hydroxyproline (OH-proline) concentration, CF and CH by echocardiography. Training improved aerobic capacity and induced CH. MiRNAs-1, 133a, and 133b were downregulated as observed in pathological CH, however, without pathological markers. MiRNA-29c expression increased in T1 (52%) and T2 (123%), correlated with a decrease in COLIAI and COLIIIAI expression in T1 (27%, 38%) and T2 (33%, 48%), respectively. MiRNA-29c was inversely correlated to OH-proline concentration (r=0.61, P<0.05). The E/A ratio increased in T2, indicating improved LV compliance. Thus, these results show that aerobic training increase miR-29 expression and decreased collagen gene expression and concentration in the heart, which is relevant to the improved LV compliance and beneficial cardiac effects, associated with aerobic high performance training.

Moderate exercise training promotes adaptations in coronary blood flow and adenosine production in normotensive rats

OBJECTIVES

Aerobic exercise training prevents cardiovascular risks. Regular exercise promotes functional and structural adaptations that are associated with several cardiovascular benefits. The aim of this study is to investigate the effects of swimming training on coronary blood flow, adenosine production and cardiac capillaries in normotensive rats.

METHODS

Wistar rats were randomly divided into two groups: control (C) and trained (T). An exercise protocol was performed for 10 weeks and 60 min/day with a tail overload of 5% bodyweight. Coronary blood flow was quantified with a color microsphere technique, and cardiac capillaries were quantified using light microscopy. Adenine nucleotide hydrolysis was evaluated by enzymatic activity, and protein expression was evaluated by western blot. The results are presented as the means ± SEMs (p<0.05).

RESULTS

Exercise training increased the coronary blood flow and the myocardial capillary-to-fiber ratio. Moreover, the circulating and cardiac extracellular adenine nucleotide hydrolysis was higher in the trained rats than in the sedentary rats due to the increased activity and protein expression of enzymes, such as E-NTPDase and 59'-nucleotidase.

CONCLUSIONS

Swimming training increases coronary blood flow, number of cardiac capillaries, and adenine nucleotide hydrolysis. Increased adenosine production may be an important contributor to the enhanced coronary blood flow and angiogenesis that were observed in the exercise-trained rats; collectively, these results suggest improved myocardial perfusion.