The effect of phosphate and calcium on force generation in glycerinated rabbit skeletal muscle fibers. A steady-state and transient kinetic study

Millar, N C; Homsher, Earl

doi:10.1016/s0021-9258(17)30494-5

Cited by 279 publications

(91 citation statements)

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“…However, k Pi is approximately twofold faster than k tr in fibers under the same conditions, indicating that some process preceding the force-generating isomerization is limiting k tr . This hypothesis is supported by the finding that increasing [Ca 2ϩ ] and [P i ] both increase k tr , whereas k Pi increases with increasing [P i ], but is essentially independent of [Ca 2ϩ ] (Millar and Homsher, 1990;Regnier et al, 1995). Furthermore, experiments using nucleotide analogs of ATP (nucleoside triphosphates or NTPs) as substrates for muscle contractions suggest that the kinetics of force development can be influenced by the rate of nucleotide binding to and cleavage by myosin, which occurs before the force-generating step (Pate et al, 1993;White et al, 1993;Regnier et al, 1998b).…”

Section: Introductionmentioning

confidence: 75%

“…Force and stiffness are designated, respectively, as P o and S o for ATP and as P NTP and S NTP for analogs of ATP, respectively. Force transients were acquired at 20 kHz and analyzed using the program KFIT (Millar and Homsher, 1990). Fibers were excluded if the control isometric force decreased by Ͼ10% during the course of the experiment.…”

Section: Fiber Preparation Solutions and Mechanical Measurementsmentioning

confidence: 99%

“…Fibers were excluded if the control isometric force decreased by Ͼ10% during the course of the experiment. Measurements of k tr were made as previously described (Brenner and Eisenberg, 1986;Brenner, 1988;Millar and Homsher, 1990). After the development of steady-state force, the fiber was allowed to shorten by applying a rapid, shortening length step of 10 -15% L o , usually for 30 -40 ms. After this period of shortening, the fiber was restretched to its original length, and the rate of force redevelopment after the rapid, transient force spike was measured using a single-exponential fit.…”

Section: Fiber Preparation Solutions and Mechanical Measurementsmentioning

confidence: 99%

“…Although much is known about actomyosin ATPase in solution, the kinetic processes in muscle fibers probably differ, owing to steric constraints imposed by the orderly array of thin and thick filaments and cross-bridge strain. When the concentration of inorganic phosphate (P i ) in contracting single skinned skeletal muscle fibers is suddenly increased by photolysis of caged P i , the force exerted by the fiber decreases at a rate (k Pi ) that increases with the postphotolysis [P i ] (Millar and Homsher, 1990;Dantzig et al, 1992;Walker et al, 1992;Araujo and Walker, 1996). This behavior suggested the following kinetic scheme: Scheme 1 where force is produced by an isomerization of the crossbridge from a non-force-producing to a force-producing state and is rapidly followed and stabilized by the dissociation of P i from the cross-bridge.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of ATP Analogs on Posthydrolytic and Force Development Steps in Skinned Skeletal Muscle Fibers

Regnier¹,

Homsher

1998

Biophysical Journal

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ATP, 2-deoxy ATP (dATP), CTP, and UTP support isometric force and unloaded shortening velocity (Vu) to various extents (Regnier et al., Biophys. J. 74:3044-3058). Vu correlated with the rate of cross-bridge dissociation after the power stroke and the steady-state hydrolysis rate in solution, whereas force was modulated by NTP binding and cleavage. Here we studied the influence of posthydrolytic cross-bridge steps on force and fiber shortening by measuring isometric force and stiffness, the rate of tension decline (kPi) after Pi photogeneration from caged Pi, and the rate of tension redevelopment (ktr) after a sudden release and restretch of fibers. The slope of the force versus [Pi] relationship was the same for ATP, dATP, and CTP, but for UTP it was threefold less. ktr and kPi increased with increasing [Pi] with a similar slope for ATP, dATP, and CTP, but had an increasing magnitude of the relationship ATP < dATP < CTP. UTP reduced ktr but increased kPi. The results suggest that the rate constant for the force-generating isomerization increases with the order ATP < dATP < CTP < UTP. Simulations using a six-state model suggest that increasing the force-generating rate accounts for the faster kPi in dATP, CTP, and UTP. In contrast, ktr appears to be strongly affected by the rates of NTP binding and cleavage and the rate of the force-generating isomerization.

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Section: Introductionmentioning

confidence: 75%

Section: Fiber Preparation Solutions and Mechanical Measurementsmentioning

confidence: 99%

Section: Fiber Preparation Solutions and Mechanical Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Effect of ATP Analogs on Posthydrolytic and Force Development Steps in Skinned Skeletal Muscle Fibers

Regnier¹,

Homsher

1998

Biophysical Journal

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“…Evidence from skinned single muscle fibres demonstrates that elevated P i levels significantly reduce force (Millar & Homsher, 1990;Pate & Cooke, 1989), which is consistent with the idea that the accumulation of P i may interfere with cross-bridge cycling in sarcoplasm, and thus impact the contractile properties of skeletal muscle. These experiments however, were performed at low temperatures and evidence suggests that the depressive effect of P i may differ at more physiological temperatures.…”

Section: Peripheral Muscle Fatiguesupporting

confidence: 80%

Effects of respiratory muscle endurance training on cerebral oxygenation and hemodynamics, and effort perceptions during maximal exercise

Somerville¹

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The primary objective of this study was to investigate the effects of a 4-week respiratory muscle endurance training (eRMT) program on the physiological and psychological aspects of central fatigue using, respectively, near-infrared spectroscopy (NIRS) and quantification of effort perceptions during maximal exercise. A secondary objective was to assess any impact of eRMT on respiratory health and exercise performance. This study compared pre- and post-eRMT data from the same group of healthy adults. The results indicated that eRMT did not have any effect on respiratory function, exercise time to exhaustion, or physiological responses to exercise but significantly decreased ratings of perceived exertion (RPE) during exercise. An increase in the concentrations of oxygenated hemoglobin [O2Hb], deoxygenated hemoglobin [HHb], and total hemoglobin [tHb] during exercise was observed post-eRMT compared to pre-eRMT, and this increase differed by hemisphere. Based on these preliminary findings, we suggest an eRMTinduced left-to-right hemodynamic shift during exercise, consistent with the change from a novel to a learned task.

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Force relaxation and thin filament protein phosphorylation during acute myocardial ischemia

Han

Ogut

2010

Cytoskeleton

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Ischemia impairs myocardial function and may contribute to the progression of heart failure. In this study, rats subjected to acute ischemia demonstrated reduced Ca 2+ activated force as well as a decrease in myosin binding protein-C, titin and Ser23/24 phosphorylation of troponin I (TnI). All three proteins have been demonstrated to be downstream targets of β-adrenergic receptor activation (β-AR), leading to the hypothesis that decreased β-AR during ischemia leads to reduced protein phosphorylation and reduced rate constants of force relaxation. To test this hypothesis, force relaxation transients were recorded from permeabilized perfused and ischemic rat heart fibers following photolysis of the caged chelator diazo-2. Relaxation transients were best fit by double exponential functions whereby the majority (>70%) of the force decline was described by the fast rate constant, which was ~5 times faster than the slow rate constant. However, rate constants of relaxation between perfused and ischemic fibers were not different, despite significant decreases in sarcomeric protein phosphorylation in ischemic fibers. Treatment of perfused fibers with a cAMP analog increased Ser23/24 phosphorylation of TnI, yet the rate constants of relaxation remained unchanged. Interestingly, similar treatment of ischemic fibers did not impact TnI phosphorylation or force relaxation transients. Therefore, acute ischemia does not influence the rate constants of relaxation of permeabilized fibers. These results also suggest that the physiological level of sarcomeric protein phosphorylation is unlikely to be the primary driver of relaxation kinetics in permeabilized cardiac muscle fibers.

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The effect of phosphate and calcium on force generation in glycerinated rabbit skeletal muscle fibers. A steady-state and transient kinetic study

Cited by 279 publications

References 50 publications

The Effect of ATP Analogs on Posthydrolytic and Force Development Steps in Skinned Skeletal Muscle Fibers

The Effect of ATP Analogs on Posthydrolytic and Force Development Steps in Skinned Skeletal Muscle Fibers

Effects of respiratory muscle endurance training on cerebral oxygenation and hemodynamics, and effort perceptions during maximal exercise

Force relaxation and thin filament protein phosphorylation during acute myocardial ischemia

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