Effects of Aerobic Training on the Cardiomyocytes of the Right Atrium of Mice

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.

Comparison of ANP and BNP Granular Density in Atria of Rats After Physiological and Pathological Hypertrophy

“…1,2 In contrast, aerobic exercise in mice augments PN granule production, natriuretic peptide expression, and secretory activity in the RA. 22 The differential changes in PG mean surface area and granule size distribution likely reflect the physiological differences between exercise and PPARγ agonism–induced cardiac hypertrophy, demonstrating that the effects of exercise, at least after four weeks, stimulate more rapid turnover of natriuretic PGs in the RA, while PPARγ agonism affects both LA and RA granule characteristics. The lack of evidence of myocardial and collagen degeneration in swim-trained rats that exhibited 15% cardiac hypertrophy 1 is suggestive of an exercise-inductive protective effect reflective in the peptide and granule morphology of the swim-trained rats.…”

“…1 In contrast, chronic exercise in rats failed to result in persistent measurable increases in circulating NT-proANP and NT-proBNP concentrations. Exercise, 21,22 and drug overload, [23][24][25] in part through the differential expression and secretion of natriuretic peptides, points out a unique distribution in peptide population resulting from different stresses that cause cardiac hypertrophy. In summary, serum natriuretic peptides serve as differential translational biomarkers between drug-and exercise-induced pathological and physiological cardiac hypertrophy.…”