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Int J Sports Med 1981; 02(3): 171-177
DOI: 10.1055/s-2008-1034606
© Georg Thieme Verlag Stuttgart · New York

Fluid Shifts from Myofibrillar to Sarcoplasmic Space in the Myocardium of Exhausted Rats*

D. P. Thomas, P. A. Molé
  • Biokinetics Research Laboratory and Section of Cardiology, Department of Medicine, Temple University Health Sciences Center, Philadelphia, PA 19140 USA
* The research was supported in part by NIH Grant HL 19425.
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Publication Date:
14 March 2008 (online)

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Abstract

Integrity of the myocardium following a swim to exhaustion (STE) was assessed by quantitative light and electron microscopy in young adult female rats. Myocardial fiber diameter and mitochondrial (MITO) number, size, and volume fraction (VF) were unaffected by the STE. Also, the STE did not alter ventricular water content. In contrast, myofibrillar (MYO) VF was reduced and sarcoplasmic (SARCO) VF elevated (both P < 0.05) at exhaustion. As both cell and MITO absolute volume were apparently unchanged at exhaustion, an intracellular fluid shift from MYO to SARCO space must have occurred, without affecting MITO volume. Neither swim training nor low-protein diet modified these exhaustion-induced changes. These data provide a possible explanation at the ultrastructural level for the documented reduction in performance of the heart in the exhausted state.

Key words

exhaustion - heart - mitochondria - myofibrils - sarcoplasm - training - low-protein diet

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