Effect of voluntary exercise on number and volume of cardiomyocytes and their mitochondria in the mouse left ventricle |
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| Authors: | Judith Christina Eisele Inga-Marie Schaefer Jens Randel Nyengaard Heiner Post David Liebetanz Annemarie Brüel " target="_blank">Christian Mühlfeld |
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| Institution: | 1.Dept. of Anatomy,University of G?ttingen,G?ttingen,Germany;2.Stereology and Electron Microscopy Research Laboratory,University of ?rhus,?rhus,Denmark;3.Dept. of Cardiology and Pulmonary Medicine,University of G?ttingen,G?ttingen,Germany;4.Dept. of Clinical Neurophysiology,University of G?ttingen,G?ttingen,Germany;5.Institute of Anatomy,University of ?rhus,?rhus,Denmark;6.Institute of Anatomy, Division of Histology,University of Bern,Bern,Switzerland;7.Universit?t Bern, Institut für Anatomie Abteilung Histologie,Bern 9,Schweiz |
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| Abstract: | Voluntary exercise (VE) has a beneficial influence on the heart and mean lifespan. The present study evaluates structural
adaptations of cardiomyocytes and their mitochondria due to VE by new, unbiased stereological methods. Female, 7–9-week-old
mice were randomly assigned to a control (CG, n = 7) or VE group (EG, n = 7). EG animals were housed in cages with free access to a running wheel and had a mean running distance of 6.7 (1.8) km
per day. After 4 weeks, the hearts of all mice were processed for light and electron microscopy. We estimated the number and
volume of cardiomyocytes by the disector method and the number and volume of mitochondria by estimation of the Euler number.
In comparison to CG, VE did not have an effect on the myocardial volume of the left ventricle (CG: 93 (10), EG: 103 (17) (mm3)), the number of cardiomyocytes (CG: 2.81 (0.27), EG: 2.82 (0.43) (×106)) and their number-weighted mean volume. However, the composition of the cardiomyocytes changed due to VE. The total volume
of mitochondria (CG: 21.8 (4.9), EG: 32.2 (4.3) (mm3), P < 0.01) and the total number (CG: 3.76 (0.44), EG: 7.02 (1.13) (×1010), P < 0.001) were significantly higher in EG than in CG. The mean number-weighted mitochondrial volume was smaller in EG than
in CG (P < 0.05). In summary, VE does not alter ventricular volume nor cardiomyocyte volume or number but the oxidative capacity of
cardiomyocytes by an increased mitochondrial number and total volume in the left ventricle. These structural changes may participate
in the beneficial effects of VE.
Returned for 1. revision: 12 January 2007 1. Revision received: 17 January 2007 Returned for 2. revision: 12 February 2007
2. Revision received: 27 September 2007 |
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| Keywords: | stereology myocardium Euler number hypertrophy electron microscopy |
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