Abstract
ABSTRACT Introduction: Polypeptide hormones (natriuretic peptides, NPs) are secreted by the cardiac atria and play an important role in the regulation of blood pressure. Objective: To evaluate the effects of aerobic training on the secretory apparatus of NPs in cardiomyocytes of the right atrium. Methods: Nine-month-old mice were divided in two groups (n=10): control group (CG) and trained group (TG). The training protocol was performed on a motor treadmill for 8 weeks. Systolic blood pressure was measured at the beginning of the experiment (9 months of age) and at moment of the sacrifice (11 months of age). Electron micrographs were used to quantify the following variables: the quantitative density and area of NP granules, the relative volumes of the mitochondria, endoplasmic reticulum, and Golgi complex and the relative volume of euchromatin in the nucleus and the number of pores per 10 µm of the nuclear membrane. The results were compared by Student's t test (p< 0.05). Results: The cardiomyocytes obtained from TG mice showed increased density and sectional area of secretory granules of NP, higher relative volume of endoplasmic reticulum, mitochondria, and Golgi complex compared with the CG mice. Furthermore, the quantitative density of nuclear pores and the relative volume of euchromatin in the nucleus were significantly higher compared with the CG mice. Conclusion: Aerobic training caused hypertrophy of the secretory apparatus in the cardiomyocytes of right atrium, which could explain the intense synthesis of natriuretic peptides in trained mice with respect to the untrained mice.
Highlights
Polypeptide hormones are secreted by the cardiac atria and play an important role in the regulation of blood pressure
The cardiomyocytes obtained from trained group (TG) mice showed increased density and sectional area of secretory granules of Natriuretic peptides (NPs), higher relative volume of endoplasmic reticulum, mitochondria, and Golgi complex compared with the control group (CG) mice
The second objective of this work was to evaluate the quantitative effects of aerobic training on the secretory apparatus of the atrium cardiomyocytes, including the number of pores per 10 μm of nuclear membrane, the relative volumes (%) of euchromatin, mitochondria, endoplasmic reticulum and Golgi complex in the cardiomyocytes of the trained mice compared with sedentary controls
Summary
Polypeptide hormones (natriuretic peptides, NPs) are secreted by the cardiac atria and play an important role in the regulation of blood pressure. Results: The cardiomyocytes obtained from TG mice showed increased density and sectional area of secretory granules of NP, higher relative volume of endoplasmic reticulum, mitochondria, and Golgi complex compared with the CG mice. The production and secretion of NPs depend on the structural components of the atrium cardiomyocytes including the Golgi apparatus, mitochondria, endoplasmic reticulum, the euchromatin and the number of pores in the nuclear membrane[3]. The second objective of this work was to evaluate the quantitative effects of aerobic training on the secretory apparatus of the atrium cardiomyocytes, including the number of pores per 10 μm of nuclear membrane, the relative volumes (%) of euchromatin, mitochondria, endoplasmic reticulum and Golgi complex in the cardiomyocytes of the trained mice compared with sedentary controls.
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