Effects of Growth Hormone on Cardiac Remodeling During Resistance Training in Rats

Telocytes response to cardiac growth induced by resistance exercise training and endurance exercise training in adult male rats

Telocytes are interstitial cells found in different tissues, including cardiac stem cell niches. The purpose of this study was to investigate the response of the telocytes to the cardiac growth that occurs in response to resistance and endurance exercise trainings using rats distributed into control, endurance, and resistance training groups. Results revealed that the ratio of heart weight to body weight, cardiomycyte number, cardiomyocyte area, thickness of the left ventricular wall were significantly higher in the training groups compared to the control group. We observed increment in the cardiomyocytes surface area and thickness of the left ventricular wall in the resistance-training group than endurance-training group. We conclude that both resistance and endurance exercise trainings will lead to an increased number of cardiac telocytes, consequently, promote activity of the cardiac stem cells, and results in physiological cardiac growth, and this response does not seem to depend on the type of exercise.

EFFECT OF AEROBIC AND ANAEROBIC TRAINING ON DIFFERENT ERGOMETERS IN RAT MUSCLE AND HEART TISSUES

Objective

Analyze the effects of aerobic and anaerobic training on different ergometers on muscle and cardiac hypertrophy in rats.

Methods

The animals were separated into the following groups: Control (C), Aerobic Training in Water (ATW), Resistance Training in Water (RTW), Aerobic Training on Treadmill (ATT), and Resistance Training in Climbing (RTC). All training protocols were carried out for 4 weeks, 3 times/week. The cross-sectional area (CSA) of the gastrocnemius muscle cells and the areas of the cardiomyocytes were measured.

Results

In the fast-twitch fibers, there was an increase in CSA in the RTW and RTC groups compared to the ATW (p<0.01 and p<0.01) and ATT groups (p<0.01 and p<0.01). In the slow-twitch fibers, the ATW and ATT groups demonstrated a lower CSA compared to the RTW (p=0.03 and p<0.00) and RTC groups (p<0.01 and p<0.01). In the cardiomyocytes, there was an increase in the area of the RTW and RTC groups compared to groups C (p<0.01; p<0.01), ATW (p=0.02; p<0.01), and ATT (p<0.01; p<0.01).

Conclusion

The anaerobic training effectively promotes hypertrophy in the fast-twitch fibers and the cardiomyocytes. Level of Evidence V; Animal experimental study .

Effect of different doses of 2,4-dichlorophenoxyacetic acid (2,4-D) on cardiac parameters in male Wistar rats

The objective of this study was to evaluate the effects of different doses of 2,4-dichlorophenoxyacetic herbicide in rat hearts. Exposure was through rat food that was nebulized with the herbicide. Thirty adult male Wistar rats (200-300 g) were used. The diet was exposed to 2,4-D in two different doses (CG: control group 10 ml distilled water; LCG: low concentration group 3.71 × 10^-3 g.ia/ha diluted in 10 ml saline at 0.9% and HCG: High concentration group 9.28 × 10^-3 g.ia/ha diluted in 10 ml 0.9% saline). After 6 months of exposure, blood samples were collected for CKMB evaluation, and left ventricular fragments were analyzed by histological evaluation, fibrosis measurements, fractal dimension and immunohistochemistry (BAX, Bcl2, TNF-α and NF-kB). There were no significant changes in CK-MB concentration, histological parameters, fibrosis measurements and fractal dimension. Long-term oral consumption of food nebulized by the herbicide 2,4-D promoted an increase in BAX, Bcl-2/BAX, and cytoplasmic NF-kB in the nuclear area of the group that received the highest dose of the herbicide. This suggests that the herbicide induces cardiotoxicity.

Cardiovascular Adaptations Induced by Resistance Training in Animal Models

In the last 10 years the number of studies showing the benefits of resistance training (RT) to the cardiovascular system, have grown. In comparison to aerobic training, RT-induced favorable adaptations to the cardiovascular system have been ignored for many years, thus the mechanisms of the RT-induced cardiovascular adaptations are still uncovered. The lack of animal models with comparable protocols to the RT performed by humans hampers the knowledge. We have used squat-exercise model, which is widely used by many others laboratories. However, to a lesser extent, other models are also employed to investigate the cardiovascular adaptations. In the subsequent sections we will review the information regarding cardiac morphological adaptations, signaling pathway of the cardiac cell, cardiac function and the vascular adaptation induced by RT using this animal model developed by Tamaki et al. in 1992. Furthermore, we also describe cardiovascular findings observed using other animal models of RT.