Myocardial Efficiency and Economy in Huxley's 1957 Crossbridge Model.
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概要
- 論文の詳細を見る
In cardiac muscle and the heart, the maximum mechanical efficiency is relatively constant (15-25%) under various acute and chronic inotropic interventions, whereas the economy of isometric force development varies by 2-4 times with these interventions. We speculated about this discrepancy using Huxley's 1957 crossbridge model. Our theoretical derivation showed that the economy is proportional to the product of the thermodynamic efficiency (w/e in Huxley's notation) and the reciprocal of the rate constant of crossbridge detachment in the forward position (g1 in Huxley's notation): (w/e) (l/g1). The w/e value is the maximum limit of the mechanical efficiency. This w/e value has been assumed to be 0.75 for fast contracting skeletal muscle and 0.95 for slow contracting skeletal muscle; a 1.3-fold difference. Representative g1 values are 6/s for the fast skeletal muscle and 0.12/s for the slow skeletal muscle; a 50-fold difference. These differences in w/e and g1 between the fast and slow skeletal muscles predict that the economy would change by 65 (=1.3×50) times while the efficiency changes by only 1.3 times. Extrapolation of this relation to fast and slow contracting cardiac muscles suggests that only a 4-fold change in the economy, which is the observed maximum difference between the rat or rabbit hypo- and hyperthyroid myocardium, would be associated with only a less than 10% change in the maximum mechanical efficiency.
- International Heart Journal刊行会の論文
著者
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SUGA Hiroyuki
Second Department of Physiology, Okayama University Medical School
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TAYLOR Tad
Yale School of Medicine
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SUGA Hiroyuki
Second Department of Physiology, Okayama University School of Medicine
関連論文
- Estimation of Total Carbon Dioxide Contents in Canine Coronary Arterial and Venous Whole Blood Samples
- Myocardial Efficiency and Economy in Huxley's 1957 Crossbridge Model.
- Constant Efficiency versus Variable Economy of Cardiac Contraction.