Cross-Bridge Dynamics in the Contracting Heart

Peterson, Jon N.; Alpert, Norman R.

doi:10.1007/978-1-4684-6039-1_14

Cited by 2 publications

(6 citation statements)

References 18 publications

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“…The set‐up used here, shown schematically in Fig. 1, is a new implementation of our previously described myothermal system (Peterson & Alpert, 1998). Temperature drift was under 10 −6 °C s −1 , approximately three orders of magnitude lower than the muscle signal transient.…”

Section: Methodsmentioning

confidence: 99%

“…Two‐state cross‐bridge analysis. We have extended the above standard myothermal‐mechanical analysis by considering a two‐state model of cross‐bridge cycling (Huxley, 1957; Brenner, 1988; Peterson & Alpert, 1998) where the bridge is either attached and generating force ( A ) or detached ( D ):

Cross‐bridge kinetics are defined by the apparent rate constants for attachment ( f app ) and detachment ( g app ). In the steady state, the number of attached and detached cross‐bridges remains constant.…”

Section: Methodsmentioning

confidence: 99%

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Altered cross‐bridge characteristics following haemodynamic overload in rabbit hearts expressing V₃ myosin

Peterson

Nassar

Anderson

et al. 2001

The Journal of Physiology

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Cardiac performance in systole and diastole is critically dependent upon the underlying characteristics of the cross-bridge cycle. Myosin cross-bridges extending out from the thick filament produce muscle force and motion via repetitive interactions with actin-containing thin filaments, with the obligatory hydrolysis of ATP.The failing human heart exhibits a 100 % greater crossbridge force-time integral (FTI XBr ) than normal (Hasenfuss et al. 1991) and a decrease in myofibrillar ATPase activity (Alpert & Gordon, 1962;Pagani et al. 1988) with no change in the myosin heavy chain (MHC) isoform profile (100 % V 3 ; Schiaffino & Reggiani, 1996). The FTI XBr and ATPase activity are both accepted measures of cross-bridge performance, where the former is an index of mechanical response per molecule of ATP hydrolysed, while the latter is an index of interaction kinetics. The mechanisms underlying these mechanical and kinetic alterations in the human heart are unknown, though a shift in cardiac troponin T (cTnT) isoform expression has been observed to correlate with the decrease in myofibrillar ATPase activity (Anderson et al. 1991).In the rabbit heart, surgically induced right ventricular pressure overload (PO) results in a two-fold increase in the isometric FTI XBr (Hasenfuss et al. 1991), along with a reduction in shortening velocity (Hamrell & Dey, 1993) and ATPase activity (Maughan et al. 1979;Litten et al. 1982). These changes are accompanied by a relatively subtle myosin isoform shift from 88 % V 3 to 100 % V 3 (Litten et al. 1982Hasenfuss et al. 1991). This raises the possibility that, as in the failing human heart, modulatory mechanisms independent of the MHC composition may be important in the haemodynamically stressed rabbit. 1. Our goal in this study was to evaluate the effect of haemodynamic overload on cross-bridge (XBr) kinetics in the rabbit heart independently of myosin heavy chain (MHC) isoforms, which are known to modulate kinetics in small mammals. We applied a myothermal-mechanical protocol to isometrically contracting papillary muscles from two rabbit heart populations: (1) surgically induced right ventricular pressure overload (PO), and (2) sustained treatment with propylthiouracil (PTU). Both treatments resulted in a 100 % V 3 MHC profile.2. XBr force-time integral (FTI), evaluated during the peak of the twitch from muscle FTI and tension-dependent heat, was greater in the PO hearts (0.80 ± 0.10 versus 0.45 ± 0.05 pN s, means ± S.E.M., P = 0.01).3. Within the framework of a two-state XBr model, the PO XBr developed more force while attached (5.8 ± 0.9 versus 2.7 ± 0.3 pN), with a lower cycling rate (0.89 ± 0.10 versus 1.50 ± 0.14 s _1) and duty cycle (0.14 ± 0.03 versus 0.24 ± 0.02).4. Only the ventricular isoforms of myosin light chain 1 and 2 and cardiac troponin I (cTnI) were expressed, with no difference in cTnI phosphorylation between the PO and PTU samples. The troponin T (TnT) isoform compositions in the PO and PTU samples were significantly different (P = 0.001), with TnT 2 comprising 2.29...

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Altered cross‐bridge characteristics following haemodynamic overload in rabbit hearts expressing V₃ myosin

Peterson

Nassar

Anderson

et al. 2001

The Journal of Physiology

Self Cite

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show abstract

“…Red leƩers -sequence specific to β-myosin of small mammals, Black leƩers -specific to β-myosin of large mammals. Blue leƩers -specific to the human isoform myosin [119,121,122]. No difference in the average force per crossbridge was detected [122].…”

Section: Myofibrils/myocytes Expressing α-Vs β-Myosinmentioning

confidence: 97%

“…Blue leƩers -specific to the human isoform myosin [119,121,122]. No difference in the average force per crossbridge was detected [122].…”

Section: Myofibrils/myocytes Expressing α-Vs β-Myosinmentioning

confidence: 97%

“…Attempts made to estimate α and β cross-bridge dynamics from intact multicellular cardiac preparations took advantage of the α/β-isoform shift that had been described following treatment with agents capable of modifying the thyroid state of animal models (usually, rabbit or rat; see above). The mechanical [ 27 , 34 , 119 , 120 ], myothermal (rabbit [ 121 , 122 ]), and ATPase behaviors [ 27 ] of papillary muscles of known α- and β-myosin isoform composition were then compared. Note that in these earlier studies, the myosin isoforms were referred to as V1-α, V3-β and V2 intermediate.…”

Section: Myofibrils/myocytes Expressing α- Vs β-Myosinmentioning

confidence: 99%

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Alpha and beta myosin isoforms and human atrial and ventricular contraction

Walklate

Ferrantini

Johnson

et al. 2021

Cell. Mol. Life Sci.

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Human atrial and ventricular contractions have distinct mechanical characteristics including speed of contraction, volume of blood delivered and the range of pressure generated. Notably, the ventricle expresses predominantly β-cardiac myosin while the atrium expresses mostly the α-isoform. In recent years exploration of the properties of pure α- & β-myosin isoforms have been possible in solution, in isolated myocytes and myofibrils. This allows us to consider the extent to which the atrial vs ventricular mechanical characteristics are defined by the myosin isoform expressed, and how the isoform properties are matched to their physiological roles. To do this we Outline the essential feature of atrial and ventricular contraction; Explore the molecular structural and functional characteristics of the two myosin isoforms; Describe the contractile behaviour of myocytes and myofibrils expressing a single myosin isoform; Finally we outline the outstanding problems in defining the differences between the atria and ventricles. This allowed us consider what features of contraction can and cannot be ascribed to the myosin isoforms present in the atria and ventricles.

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Cross-Bridge Dynamics in the Contracting Heart

Cited by 2 publications

References 18 publications

Altered cross‐bridge characteristics following haemodynamic overload in rabbit hearts expressing V₃ myosin

Altered cross‐bridge characteristics following haemodynamic overload in rabbit hearts expressing V₃ myosin

Alpha and beta myosin isoforms and human atrial and ventricular contraction

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Cross-Bridge Dynamics in the Contracting Heart

Cited by 2 publications

References 18 publications

Altered cross‐bridge characteristics following haemodynamic overload in rabbit hearts expressing V3 myosin

Altered cross‐bridge characteristics following haemodynamic overload in rabbit hearts expressing V3 myosin

Alpha and beta myosin isoforms and human atrial and ventricular contraction

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Altered cross‐bridge characteristics following haemodynamic overload in rabbit hearts expressing V₃ myosin

Altered cross‐bridge characteristics following haemodynamic overload in rabbit hearts expressing V₃ myosin