scholarly journals Suppression of muscle contraction by vanadate. Mechanical and ligand binding studies on glycerol-extracted rabbit fibers.

1985 ◽  
Vol 86 (3) ◽  
pp. 305-327 ◽  
Author(s):  
J A Dantzig ◽  
Y E Goldman
Keyword(s):  
Muscle Fibers ◽  
Adenosine Diphosphate ◽  
Order Rate Constant ◽  
Rabbit Muscle ◽  
Binding Studies ◽  
Tension Development ◽  
Cross Bridge ◽  
Initial Rise ◽  
Cross Bridges ◽  
Myosin X

The suppression of tension development by orthovanadate (Vi) was studied in mechanical experiments and by measuring the binding of radioactive Vi and nucleotides to glycerol-extracted rabbit muscle fibers. During active contractions, Vi bound to the cross-bridges and suppressed tension with an apparent second-order rate constant of 1.34 X 10(3) M-1s-1. The half-saturation concentration for tension suppression was 94 microM Vi. The incubation of fibers in Vi relaxing or rigor solutions prior to initiation of active contractions had little effect on the initial rise of active tension. The addition of adenosine diphosphate (ADP) and Vi to fibers in rigor did not cause relaxation. Suppression of tension only developed during cross-bridge cycling. After slow relaxation from rigor in 1 mM Vi and low (50 microM) MgATP concentration (0 Ca2+), radioactive Vi and ADP were trapped within the fiber. This finding indicated the formation of a stable myosin X ADP X Vi complex, as has been reported in biochemical experiments with isolated myosin. Vi and ADP trapped within the fibers were released only by subsequent cross-bridge attachment. Vi and ADP were preferentially trapped under conditions of cross-bridge cycling in the presence of ATP rather than in relaxed fibers or in rigor with ADP. These results indicate that in the normal cross-bridge cycle, inorganic phosphate (Pi) is released from actomyosin before ADP. The resulting actomyosin X ADP intermediate can bind Vi and Pi. This intermediate probably supports force. Vi behaves as a close analogue of Pi in muscle fibers, as it does with isolated actomyosin.

Regulation of the cross-bridge transition from a weakly to strongly bound state in skinned rabbit muscle fibers

1995 ◽  
Vol 269 (6) ◽  
pp. C1532-C1539 ◽  
Author(s):  
M. Regnier ◽  
C. Morris ◽  
E. Homsher
Keyword(s):  
Muscle Fibers ◽  
Bound State ◽  
Single Step ◽  
Rabbit Muscle ◽  
Weakly Bound ◽  
Cross Bridge ◽  
Skinned Muscle ◽  
Butanedione Monoxime ◽  
Bridge Models ◽  
Parallel Fashion

The regulation of cross-bridge transition from weakly attached to force-bearing states was studied at 10 degrees C in skinned muscle fibers by measuring the rate of force development after a quick release-restretch cycle (ktr), the rate of force decline (kPi) after photogeneration of Pi from caged Pi, and stiffness in the presence and absence of an inhibitor of strong cross-bridge formation, 2,3-butanedione monoxime (BDM). Both BDM and Pi suppressed force more than stiffness. However, reduction of Ca2+ suppressed force and stiffness in a parallel fashion. Both ktr and kPi were reversibly reduced (by 30-35%) in 3 mM BDM, but both were increased by increasing Pi concentration. Reduction of Ca2+ concentration to match the force seen in 3 mM BDM had no effect on kPi but decreased ktr by 85%. These results are inconsistent with cross-bridge models undergoing the transition from a weakly bound to a force-generating state in a single step but are consistent with a model having two steps, one of which is controlled by pCa.

Effect of Pi on unloaded shortening velocity of slow and fast mammalian muscle fibers

2002 ◽  
Vol 282 (4) ◽  
pp. C647-C653 ◽  
Author(s):  
Jeffrey J. Widrick
Keyword(s):  
Fiber Type ◽  
Muscle Fibers ◽  
Medial Gastrocnemius ◽  
Type I ◽  
Shortening Velocity ◽  
Cross Bridge ◽  
Skinned Muscle ◽  
Specific Effects ◽  
Cross Bridges ◽  
Bridge Models

Chemically skinned muscle fibers, prepared from the rat medial gastrocnemius and soleus, were subjected to four sequential slack tests in Ca2+-activating solutions containing 0, 15, 30, and 0 mM added Pi. Pi (15 and 30 mM) had no effect on the unloaded shortening velocity ( V o) of fibers expressing type IIb myosin heavy chain (MHC). For fibers expressing type I MHC, 15 mM Pi did not alter V o, whereas 30 mM Pireduced V o to 81 ± 1% of the original 0 mM Pi value. This effect was readily reversible when Pi was lowered back to 0 mM. These results are not compatible with current cross-bridge models, developed exclusively from data obtained from fast fibers, in which V o is independent of Pi. The response of the type I fibers at 30 mM Pi is most likely the result of increased internal drag opposing fiber shortening resulting from fiber type-specific effects of Pi on cross bridges, the thin filament, or the rate-limiting step of the cross-bridge cycle.

scholarly journals Mechanical transients initiated by photolysis of caged ATP within fibers of insect fibrillar flight muscle.

1991 ◽  
Vol 98 (4) ◽  
pp. 657-679 ◽  
Author(s):  
M Yamakawa ◽  
Y E Goldman
Keyword(s):  
Rate Constant ◽  
Time Course ◽  
Flight Muscle ◽  
Order Rate Constant ◽  
Stretch Activation ◽  
Pulse Photolysis ◽  
Caged Atp ◽  
Cross Bridge ◽  
The Cross ◽  
Cross Bridges

Kinetics of the cross-bridge cycle in insect fibrillar flight muscle have been measured using laser pulse photolysis of caged ATP and caged inorganic phosphate (Pi) to produce rapid step increases in the concentration of ATP and Pi within single glycerol-extracted fibers. Rapid photochemical liberation of 100 microM-1 mM ATP from caged ATP within a fiber caused relaxation in the absence of Ca2+ and initiated an active contraction in the presence of approximately 30 microM Ca2+. The apparent second order rate constant for detachment of rigor cross-bridges by ATP was between 5 x 10(4) and 2 x 10(5) M-1s-1. This rate is not appreciably sensitive to the Ca2+ or Pi concentrations or to rigor tension level. The value is within an order of magnitude of the analogous reaction rate constant measured with isolated actin and insect myosin subfragment-1 (1986. J. Muscle Res. Cell Motil. 7:179-192). In both the absence and presence of Ca2+ insect fibers showed evidence of transient cross-bridge reattachment after ATP-induced detachment from rigor, as found in corresponding experiments on rabbit psoas fibers. However, in contrast to results with rabbit fibers, tension traces of insect fibers starting at different rigor tensions did not converge to a common time course until late in the transients. This result suggests that the proportion of myosin cross-bridges that can reattach into force-generating states depends on stress or strain in the filament lattice. A steady 10-mM concentration of Pi markedly decreased the transient reattachment phase after caged ATP photolysis. Pi also decreased the amplitude of stretch activation after step stretches applied in the presence of Ca2+ and ATP. Photolysis of caged Pi during stretch activation abruptly terminated the development of tension. These results are consistent with a linkage between Pi release and the steps leading to force production in the cross-bridge cycle.

BDM affects nucleotide binding and force generation steps of the cross-bridge cycle in rabbit psoas muscle fibers

1994 ◽  
Vol 266 (2) ◽  
pp. C437-C447 ◽  
Author(s):  
Y. Zhao ◽  
M. Kawai
Keyword(s):  
Equilibrium Constants ◽  
Muscle Fibers ◽  
Psoas Muscle ◽  
Isometric Tension ◽  
Activation Mechanism ◽  
Phosphate Binding ◽  
Rabbit Psoas ◽  
Cross Bridge ◽  
The Cross ◽  
Cross Bridges

The effect of 2,3-butanedione monoxime (BDM) on elementary steps of the cross-bridge cycle was studied with the sinusoidal analysis technique in skinned rabbit psoas muscle fibers. Our results showed that isometric tension and stiffness decreased progressively with an increase in the BDM concentration. The MgATP and MgADP binding constants increased 27 and 6 times, respectively, when BDM was increased from 0 to 18 mM, whereas the phosphate binding constant did not change significantly. The equilibrium constants of the ATP isomerization and detachment step were not sensitive to BDM, whereas the equilibrium constant of the attachment (power stroke) step decreased with BDM. Thus, in the presence of BDM, the number of attached cross bridges decreases; more cross bridges accumulate in the detached state, causing isometric tension and stiffness to decline. However, our detailed analysis shows that the decrease in the number of attached cross bridges is approximately 40%, which is not adequate to account for the 84% decrease in the isometric tension when 18 mM BDM was present. Therefore we suggest that a thin-filament activation mechanism is also affected by BDM.

Measurement of activation energy and oxidative phosphorylation onset kinetics in isolated muscle fibers in the absence of cross-bridge cycling

2006 ◽  
Vol 290 (6) ◽  
pp. R1707-R1713 ◽  
Author(s):  
B. Walsh ◽  
R. A. Howlett ◽  
C. M. Stary ◽  
C. A. Kindig ◽  
M. C. Hogan
Keyword(s):  
Activation Energy ◽  
Atp Hydrolysis ◽  
Muscle Fibers ◽  
Metabolic Cost ◽  
Oxygen Uptake Kinetics ◽  
Isometric Tension ◽  
Isometric Contractions ◽  
Fiber Types ◽  
Tension Development ◽  
Cross Bridge

This study utilized N-benzyl- p-toluene sulfonamide (BTS), a potent inhibitor of cross-bridge cycling, to measure 1) the relative metabolic costs of cross-bridge cycling and activation energy during contraction, and 2) oxygen uptake kinetics in the presence and absence of myosin ATPase activity, in isolated Xenopus laevis muscle fibers. Isometric tension development and either cytosolic Ca2+ concentration ([Ca2+]c) or intracellular Po2 (P[Formula: see text]) were measured during contractions at 20°C in control conditions (Con) and after exposure to 12.5 μM BTS. BTS attenuated tension development to 5 ± 0.4% of Con but did not affect either resting or peak [Ca2+]c during repeated isometric contractions. To determine the relative metabolic cost of cross-bridge cycling, we measured the fall in P[Formula: see text] (ΔP[Formula: see text]; a proxy for V̇o2) during contractions in Con and BTS groups. BTS attenuated ΔP[Formula: see text] by 55 ± 6%, reflecting the relative ATP cost of cross-bridge cycling. Thus, extrapolating ΔP[Formula: see text] to a value that would occur at 0% tension suggests that actomyosin ATP requirement is ∼58% of overall ATP consumption during isometric contractions in mixed fiber types. BTS also slowed the fall in P[Formula: see text] (time to 63% of overall ΔP[Formula: see text]) from 75 ± 9 s (Con) to 101 ± 9 s (BTS) ( P < 0.05), suggesting an important role of the products of ATP hydrolysis in determining the V̇o2 onset kinetics. These results demonstrate in isolated skeletal muscle fibers that 1) activation energy accounts for a substantial proportion (∼42%) of total ATP cost during isometric contractions, and 2) despite unchanged [Ca2+]c transients, a reduced rate of ATP consumption results in slower V̇o2 onset kinetics.

Inhibition of cycling and noncycling cross bridges in skinned smooth muscle by vanadate

1986 ◽  
Vol 250 (2) ◽  
pp. C325-C332 ◽  
Author(s):  
R. A. Nayler ◽  
M. P. Sparrow
Keyword(s):  
Smooth Muscle ◽  
Active Site ◽  
Skinned Fibers ◽  
Cross Bridge ◽  
The Cross ◽  
High Concentrations ◽  
Cross Bridges ◽  
Myosin X ◽  
A Site ◽  
Small Inhibition

Vanadate (Vi, 3-300 microM) reversibly inhibited force development elicited by micromolar Ca2+ in membrane-skinned fibers of smooth muscle from taenia coli and trachea of guinea pig. When relaxed fibers were preincubated with Vi, the contraction to Ca2+ was characterized by a peak response followed by a lower steady-state phase. The peak phase depended on the rate of contraction and the [Vi]and was absent after Vi incubation during a previous contraction. These observations were consistent with Vi binding to a site that was exposed during the cross-bridge cycle but absent in the relaxed state. The actin X myosin X ADP intermediate formed at the active site during the cross-bridge cycle is suggested as the site of action of Vi. A weak antagonism between Pi and Vi was demonstrated during contractions activated by myosin thiophosphorylation. High concentrations of Pi (6-12 mM) were needed to produce a small inhibition (10%) of maximal Ca2+-activated tension. Skinned fibers relaxed slowly after Ca2+ removal, and the absence of an active state suggested that tension was maintained by noncycling cross bridges. Both Vi and Pi increased the rate of tension loss by 10-fold, but Vi was 5-10 times more potent than Pi. It is suggested that Vi and Pi both act on the active site but that Pi has a more efficacious action on slowly cycling than rapidly cycling cross bridges.

scholarly journals Phosphate Starvation and the Nonlinear Dynamics of Insect Fibrillar Flight Muscle

1972 ◽  
Vol 60 (3) ◽  
pp. 307-336 ◽  
Author(s):  
D. G. S. White ◽  
John Thorson
Keyword(s):  
Nonlinear Dynamics ◽  
Adenosine Triphosphate ◽  
Rate Constants ◽  
Flight Muscle ◽  
Phosphate Starvation ◽  
Adenosine Diphosphate ◽  
Cross Bridge ◽  
Nonlinear Mechanical ◽  
Cross Bridges ◽  
Mechanical Dynamics

The nonlinear mechanical dynamics of glycerinated insect fibrillar flight muscle are investigated. The most striking nonlinearity reported previously, which often resulted in oscillatory work being limited to frequencies below those of natural flight, disappears if 5 mM or more orthophosphate is added to the experimental solutions. We show that two further asymmetric nonlinearities, which remain even though phosphate is present, are predicted by cross-bridge theory if one takes account of the expected distortion of attached cross-bridges as filament sliding becomes appreciable. Adenosine triphosphate and adenosine diphosphate have opponent effects upon the mechanical rate constants, suggesting a scheme for the sequential ordering of the events comprising the cross-bridge cycle.

scholarly journals Radial forces within muscle fibers in rigor.

1981 ◽  
Vol 77 (1) ◽  
pp. 49-64 ◽  
Author(s):  
D W Maughan ◽  
R E Godt
Keyword(s):  
Muscle Fibers ◽  
Thick Filament ◽  
Longitudinal Force ◽  
Radial Force ◽  
Bathing Medium ◽  
High Molecular Weight Polymer ◽  
Molecular Weight Polymer ◽  
Cross Bridge ◽  
Radial Forces ◽  
Cross Bridges

Considering the widely accepted cross-bridge model of muscle contraction (Huxley. 1969. Science [Wash. D. C.]. 164:1356-1366), one would expect that attachment of angled cross-bridges would give rise to radial as well as longitudinal forces in the muscle fiber. These forces would tend, in most instances, to draw the myofilaments together and to cause the fiber to decrease in width. Using optical techniques, we have observed significant changes in the width of mechanically skinned frog muscle fibers when the fibers are put into rigor by deleting ATP from the bathing medium. Using a high molecular weight polymer polyvinylpyrrolidone (PVP-40; number average mol. wt. (Mn) = 40,000) in the bathing solution, we were able to estimate the magnitude of the radial forces by shrinking the relaxed fiber to the width observed with rigor induction. With rigor, fiber widths decreased up to approximately 10%, with shrinking being greater at shorter sarcomere spacing and at lower PVP concentrations. At higher PVP concentrations, some fibers actually swelled slightly. Radial pressures seen with rigor in 2 and 4% PVP ranged up to 8.9 x 10(3) N/m2. Upon rigor induction, fibers exerted a longitudinal force of approximately 1 x 10(5) N/m2 that was inhibited by high PVP concentrations (greater than or equal to 13%). In very high PVP concentrations (greater than or equal to 20%), fibers exerted an anomalous force, independent of ATP, which ranged up to 6 x 10(4) N/m2 at 60% PVP. Assuming that all the radial force is the result of cross-bridge attachment, we calculated that rigor cross-bridges exert a radial force of 0.2 x 1.2 x 10(-9) N per thick filament in sarcomeres near rest length. This force is of roughly the same order of magnitude as the longitudinal force per thick filament in rigor contraction or in maximal (calcium-activated) contraction of skinned fibers in ATP-containing solutions. Inasmuch as widths of fibers stretched well beyond overlap of thick and thin filaments decreased with rigor, other radially directed forces may be operating in parallel with cross-bridge forces.

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