Length-dependent effects on cardiac contractile dynamics are different in cardiac muscle containing α- or β-myosin heavy chain

Steven J Ford; Murali Chandra

doi:10.1016/j.abb.2012.10.011

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Length-dependent effects on cardiac contractile dynamics are different in cardiac muscle containing α- or β-myosin heavy chain

Journal article

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Length-dependent effects on cardiac contractile dynamics are different in cardiac muscle containing α- or β-myosin heavy chain

Steven J Ford and Murali Chandra

Archives of biochemistry and biophysics, Vol.535(1), pp.3-13

07/01/2013

DOI: https://doi.org/10.1016/j.abb.2012.10.011

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https://hdl.handle.net/2376/109961

PMCID: PMC3640676

PMID: 23111184

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Abstract

Myofibrils - drug effects

Phosphorylation

Calcium - metabolism

Sarcomeres - metabolism

Allosteric Regulation

Electrophoresis, Polyacrylamide Gel

Actomyosin - metabolism

Myosin Heavy Chains - metabolism

Muscle Tonus

Propylthiouracil - pharmacology

Biomechanical Phenomena

Myocardium - enzymology

Animals

Muscle Contraction

Ventricular Myosins - metabolism

Isoenzymes - metabolism

Adenosine Triphosphate - metabolism

Myocardium - metabolism

Mice

Myofibrils - metabolism

Enzyme Activation

Actomyosin crossbridges (XBs) are the fundamental source of force generation and pressure development in the myocardium. Faster kinetics are imparted on XBs comprised of the fast, α-myosin heavy chain (MHC) isoform, whereas slower kinetics are imparted on XBs comprised of the slow, β-MHC isoform. Other factors, such as sarcomere length (SL), influence XB formation, presumably acting through allosteric effects on the kinetics that regulate the XB cycle. We sought to determine whether the slower XB kinetics of β-MHC were more sensitive to such length-dependent effects than those of α-MHC. We studied the SL effects on mechanical properties of demembranated muscle fibers from normal and propylthiouracil-treated mouse hearts, which expressed predominantly α-MHC or β-MHC, respectively. Interestingly, XB detachment kinetics were more length-sensitive in β-MHC fibers, as estimated by tension cost and XB detachment rate constant (c), and as inferred by ktr. The nonlinearity in force responses to various-amplitude step-like changes in muscle length was more pronounced in β-MHC fibers. This phenomenon is attributed to a greater cooperative/allosteric mechanism in β-MHC fibers, as estimated by model parameter γ. These data suggest a mechanism whereby greater cooperative/allosteric effects impart an enhanced length-sensitivity of XB cycling kinetics in fibers containing the slower cycling β-MHC.

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Title: Length-dependent effects on cardiac contractile dynamics are different in cardiac muscle containing α- or β-myosin heavy chain
Creators: Steven J Ford - Department of Veterinary and Comparative Anatomy, Pharmacology, and Physiology VCAPP, Washington State University, 205 Wegner Hall, Pullman, WA 99164, United States. sford@vetmed.wsu.edu
Murali Chandra
Publication Details: Archives of biochemistry and biophysics, Vol.535(1), pp.3-13
Academic Unit: Integrative Physiology and Neuroscience, Department of
Publisher: United States
Grant note: R01 HL075643 / NHLBI NIH HHS R01-HL75643 / NHLBI NIH HHS
Identifiers: 99900547162601842
Language: English
Resource Type: Journal article