Comparison of elementary steps of the cross-bridge cycle in rat papillary muscle fibers expressing α- and β-myosin heavy chain with sinusoidal analysis

Masataka Kawai; Tarek S Karam; John Jeshurun Michael; Li Wang; Murali Chandra

doi:10.1007/s10974-016-9456-2

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Comparison of elementary steps of the cross-bridge cycle in rat papillary muscle fibers expressing α- and β-myosin heavy chain with sinusoidal analysis

Journal article

Peer reviewed

Comparison of elementary steps of the cross-bridge cycle in rat papillary muscle fibers expressing α- and β-myosin heavy chain with sinusoidal analysis

Masataka Kawai, Tarek S Karam, John Jeshurun Michael, Li Wang and Murali Chandra

Journal of muscle research and cell motility, Vol.37(6), pp.203-214

12/2016

DOI: 10.1007/s10974-016-9456-2

PMID: 27942960

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Abstract

In mammalian ventricles, two myosin heavy chain (MHC) isoforms have been identified. Small animals express α-MHC, whereas large animals express β-MHC, which contribute to a large difference in the heart rate. Sprague-Dawley rats possessing ~99% α-MHC were treated with propylthiouracil to result in 100% β-MHC. Papillary muscles were skinned, dissected into small fibers, and used for experiments. To understand the functional difference between α-MHC and β-MHC, skinned-fibers were activated under the intracellular ionic conditions: 5 mM MgATP, 1 mM Mg , 8 mM Pi, 200 mM ionic strength, pH 7.00 at 25 °C. Small amplitude sinusoidal length oscillations were applied in the frequency range 0.13-100 Hz (corresponding time domain: 1.6-1200 ms), and effects of Ca , Pi, and ATP were studied. The results show that Ca sensitivity was slightly less (10-15%) in β-MHC than α-MHC containing fibers. Sinusoidal analysis at pCa 4.66 (full Ca activation) demonstrated that, the apparent rate constants were 2-4× faster in α-MHC containing fibers. The ATP study demonstrated that, in β-MHC containing fibers, K (ATP association constant) was greater (1.7×), k and k (cross-bridge detachment and its reversal rate constants) were smaller (×0.6). The Pi study demonstrated that, in β-MHC containing fibers, k (rate constant of the force-generation step) and k were smaller (0.75× and 0.25×, respectively), resulting in greater K (3×). There were no differences in active tension, rigor stiffness, or K (equilibrium constant of the cross-bridge detachment step). Our study further demonstrated that there were no differences in parameters between fibers obtained from left and right ventricles, but with an exception in K (Pi association constant).

Adenosine Diphosphate - metabolism

Adenosine Triphosphate - metabolism

Animals

Calcium - metabolism

Male

Muscle Fibers, Skeletal - metabolism

Muscle Fibers, Skeletal - physiology

Myosin Heavy Chains - metabolism

Papillary Muscles - metabolism

Papillary Muscles - physiology

Phosphates - metabolism

Rats

Rats, Sprague-Dawley

Ventricular Myosins - metabolism

Details

Title: Subtitle: Comparison of elementary steps of the cross-bridge cycle in rat papillary muscle fibers expressing α- and β-myosin heavy chain with sinusoidal analysis
Creators: Masataka Kawai - University of Iowa
Tarek S Karam - University of Iowa
John Jeshurun Michael - Washington State University
Li Wang - University of Iowa
Murali Chandra - Washington State University
Resource Type: Journal article
Publication Details: Journal of muscle research and cell motility, Vol.37(6), pp.203-214
DOI: 10.1007/s10974-016-9456-2
PMID: 27942960
ISSN: 0142-4319
eISSN: 1573-2657
Grant note: DOI: 10.13039/100000968, name: American Heart Association, award: 13GRNT16810043; DOI: 10.13039/100000050, name: National Heart, Lung, and Blood Institute, award: R01-HL-075643; name: Poncin Fellowship
Language: English
Date published: 12/2016
Academic Unit: Anatomy and Cell Biology; Internal Medicine
Record Identifier: 9984284326802771

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