scholarly journals Sarco/endoplasmic reticulum Ca2+-ATPase isoforms: diverse responses to acidosis

1997 ◽  
Vol 321 (2) ◽  
pp. 545-550 ◽  
Author(s):  
Herman WOLOSKER ◽  
Joao B. T. ROCHA ◽  
Simone ENGELENDER ◽  
Rogerio PANIZZUTTI ◽  
Joari De MIRANDA ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Atp Hydrolysis ◽  
Blood Platelets ◽  
The Other ◽  
Maximal Velocity ◽  
Acidic Ph ◽  
Apparent Affinity ◽  
Maximal Activation ◽  
Kinetics Of

The effects of acidic pH on the kinetics of Ca2+-ATPase isoforms from intracellular membranes of skeletal muscle, cardiac muscle, cerebellum and blood platelets were studied. At neutral pH, all four Ca2+-ATPase isoforms exhibited similar Ca2+-concentration requirements for half-maximal rates of Ca2+ uptake and ATP hydrolysis. A decrease in the pH from 7.0 to 6.0 promoted a decrease in both the apparent affinity for Ca2+ [increasing half-maximal activation (K0.5)] and the maximal velocity (Vmax) of Ca2+ uptake. With skeletal muscle vesicles these effects were 5 to 10 times smaller than those observed with all the other isoforms. Acidification of the medium from pH 7.0 to 6.5 caused the release of Ca2+ from loaded vesicles and a decrease in the amount of Ca2+ retained by the vesicles at the steady state. With the vesicles derived from skeletal muscle these effects were smaller than for vesicles derived from other tissues. The rate of passive Ca2+ efflux from skeletal and cardiac muscle vesicles, loaded with Ca2+ and diluted in a medium containing none of the ligands of Ca2+-ATPase, was the same at pH 7.0 and 6.0. In contrast, the rate of Ca2+ efflux from cerebellar and platelet vesicles increased 2-fold after acidification of the medium. The effects of DMSO, Mg2+ with Pi and arsenate on the rate of Ca2+ efflux varied among the different preparations tested. The differences became more pronounced when the pH of the medium was decreased from 7.0 to 6.0. It is proposed that the kinetic differences among the Ca2+-ATPase isoforms may reflect different adaptations to cellular acidosis, such as that which occurs during ischaemia.

scholarly journals Adipo-Myokines: Two Sides of the Same Coin—Mediators of Inflammation and Mediators of Exercise

2013 ◽  
Vol 2013 ◽  
pp. 1-16 ◽  
Author(s):  
Silja Raschke ◽  
Jürgen Eckel
Keyword(s):  
Skeletal Muscle ◽  
Mrna Level ◽  
Cell Types ◽  
The Other ◽  
Target Tissue ◽  
Beneficial Effects ◽  
Mediators Of Inflammation ◽  
The One ◽  
Two Sides ◽  
Kinetics Of

This review summarizes the current literature regarding the most discussed contraction-regulated moykines like IL-6, IL-15, irisin, BDNF, ANGPTL4, FGF21, myonectin and MCP-1. It is suggested that the term myokine is restricted to proteins secreted from skeletal muscle cells, excluding proteins that are secreted by other cell types in skeletal muscle tissue and excluding proteins which are only described on the mRNA level. Interestingly, many of the contraction-regulated myokines described in the literature are additionally known to be secreted by adipocytes. We termed these proteins adipo-myokines. Within this review, we try to elaborate on the question why pro-inflammatory adipokines on the one hand are upregulated in the obese state, and have beneficial effects after exercise on the other hand. Both, adipokines and myokines do have autocrine effects within their corresponding tissues. In addition, they are involved in an endocrine crosstalk with other tissues. Depending on the extent and the kinetics of adipo-myokines in serum, these molecules seem to have a beneficial or an adverse effect on the target tissue.

Calcium removal kinetics of the sarcoplasmic reticulum ATPase in skeletal muscle

1997 ◽  
Vol 272 (4) ◽  
pp. C1087-C1098 ◽  
Author(s):  
E. E. Burmeister Getz ◽  
S. L. Lehman
Keyword(s):  
Skeletal Muscle ◽  
Steady State ◽  
Sarcoplasmic Reticulum ◽  
Initial Rate ◽  
Troponin C ◽  
The Other ◽  
Physiological Conditions ◽  
Initial Binding ◽  
Kinetics Of ◽  
Transient And Steady State

The models of the sarcoplasmic reticulum (SR) Ca pump used to simulate Ca kinetics in muscle fibers are simple but inconsistent with data on Ca binding or steady-state uptake. We develop a model of the SR pump that is consistent with data on transient and steady-state Ca removal and has rate constants identified under near-physiological conditions. We also develop models of the other main Ca-binding proteins in skeletal muscle: troponin C and parvalbumin. These models are used to simulate Ca transients in cut fibers during and after depolarizing pulses. Simulations using the full SR pump model are contrasted with simulations using a Michaelis-Menten (MM) approximation to SR pump kinetics. The MM pump underestimates the amount of Ca released during depolarization, underestimates the initial rate of Ca binding by the pump, and overestimates the later rate of Ca pumping. These errors are due to fast initial binding by the SR pump, which is neglected in the MM approximation.

The influence of D2O, perchlorate, and variation in temperature on the potential-dependent contractile function of frog skeletal muscle

1985 ◽  
Vol 63 (6) ◽  
pp. 693-703
Author(s):  
James G. Foulks ◽  
Lillian Morishita
Keyword(s):  
Skeletal Muscle ◽  
Contractile Function ◽  
Divalent Cations ◽  
Conformational Transitions ◽  
The Other ◽  
Frog Skeletal Muscle ◽  
Solvent Structure ◽  
Opposing Effects ◽  
Kinetics Of ◽  
Reduced Temperature

D2O and perchlorate manifest opposing effects on the contractile function of skeletal muscle (amplitude of twitches and maximum K contractures, potential dependence of contraction activation and inactivation), and when combined the influence of one may effectively antagonize that of the other. The ratio of perchlorate concentrations required to produce effects of equal intensity (e.g., twitch enhancement and restoration of maximum K contractures in media lacking divalent cations or containing a depressant concentration of a cationic amphipath) in H2O and D2O solutions was generally rather constant. These findings are compatible with the view that both agents can influence contractile function by virtue of their effects on solvent structure. In the absence of divalent cations, the effects of reduced temperature resemble those of D2O whereas the effects of increased temperature resemble those of the chaotropic anion. However, in other media, variation in temperature was found to result in additional nonsolvent effects so that low temperature could oppose rather than enhance the effects of D2O. These observations are discussed in terms of a model which postulates a role for solvent influences on the kinetics of two separate potential-dependent conformational transitions of membrane proteins which mediate the activation and inactivation of contraction in skeletal muscle.

scholarly journals The Contractile and Control Sites of Natural Actomyosin

1967 ◽  
Vol 50 (10) ◽  
pp. 2421-2435 ◽  
Author(s):  
Harvey M. Levy ◽  
Elizabeth M. Ryan
Keyword(s):  
Control System ◽  
Driving Force ◽  
Inhibitory Action ◽  
Atp Hydrolysis ◽  
The Other ◽  
Contractile System ◽  
Contraction And Relaxation ◽  
And Control ◽  
Kinetics Of ◽  
Hydrolysis Of

The various contractile and control sites of natural actomyosin gel were studied by comparing the kinetics of ATP hydrolysis with those of gel contraction, measured as an increase in turbidity. Contraction of actomyosin gel seems to require the cooperative reaction of ATP (with Mg) at two different sites. One of these sites catalyzes the hydrolysis of ATP and most probably contributes the driving force for contraction; the binding of ATP to the other site appears to break certain links that retard movement of the gel components. At limiting concentrations of ATP, the rate of contraction seems to depend on the rate of breaking these links as well as on the rate of ATP hydrolysis. But when both sites are saturated, the rate of contraction appears to be limited only by the rate of ATP hydrolysis. In addition to these two contractile sites, there are also two different control sites. At one, the relaxing site, the binding of ATP with Mg inhibits ATP hydrolysis and gel contraction. At the other, the binding of calcium activates contraction by overcoming the inhibitory action of Mg and ATP at the relaxing site. This control system—inhibition by substrate and disinhibition by calcium—can be selectively inactivated by heat and reactivated by dithiothreitol, a disulfide-reducing agent. These observations on the isolated contractile system are discussed in relation to the contraction and relaxation of muscle.

Uptake of a Series of Neutral Dipeptides Including l-Alanyl-l-Alanine, Glycylglycine and Glycylsarcosine by Hamster Jejunum in Vitro

1984 ◽  
Vol 67 (5) ◽  
pp. 541-549 ◽  
Author(s):  
D. M. Matthews ◽  
D. Burston
Keyword(s):  
Amino Acids ◽  
Free Amino ◽  
Inhibitory Effect ◽  
Progressive Increase ◽  
The Other ◽  
Uptake System ◽  
Apparent Affinity ◽  
Inhibitory Ability ◽  
Kinetics Of

1. This paper is the last of a set reporting an investigation of the kinetics of jejunal uptake and inhibitory ability of a series of neutral dipeptides, glycylglycine, l-ananyl-l-alanine, l-valyl-l-valine and l-leucyl-l-leucine, with progressively longer and more lipophilic side chains. 2. The results suggested that at pH 5, uptake of l-alanyl-l-alanine, like that of l-valyl-l-valine and l-leucyl-l-leucine, was the result of two processes, uptake of intact peptide and uptake of free amino acid released extracellularly. On the other hand, uptake of glycylglycine was entirely in the form of intact peptide. In contrast to uptake of l-valyl-l-valine and l-leucyl-l-leucine, the proportion of intact l-alanyl-l-alanine taken up by mediated transport was greatest at the lowest concentration studied and smallest at the highest concentration. 3. Taking the series of results as a whole, whereas the corresponding series of amino acids, glycine, l-alanine, l-valine and l-leucine, showed a progressive increase in apparent affinity for uptake and a decrease in Vmax., we could find no such regular progression with the peptides. 4. The results of work on inhibition of uptake of one dipeptide by another were unexpectedly complex. Examples were the very powerful inhibitory effect of l-valyl-l-valine on uptake of glycylsarcosine, not suggested by the Kt of the former peptide, and the failure of glycylsarcosine to cause complete inhibition of uptake of l-alanyl-l-alanine and l-leucyl-l-leucine, though it could completely inhibit uptake of l-valyl-l-valine. There may be more than one uptake system for intact peptides, but we cannot yet suggest an explanation for all the results on inhibitions of uptake.

Mg2+ and Mn2+ effects on membrane-bound and detergent-solubilized adenylate cyclase

1981 ◽  
Vol 59 (9) ◽  
pp. 748-756 ◽  
Author(s):  
George I. Drummond
Keyword(s):  
Skeletal Muscle ◽  
Adenylate Cyclase ◽  
Cardiac Muscle ◽  
Catalytic Site ◽  
Maximal Velocity ◽  
Regulatory Site ◽  
Muscle Enzyme ◽  
Membrane Bound ◽  
Stimulation Of

Mg2+ and Mn2+ stimulation of basal, F−, and guanyl-5′-yl imidodiphosphate (GPP(NH)P) stimulated adenylate cyclase in particulate and detergent-solubilized preparations of skeletal muscle, cardiac muscle, and erythrocytes was examined. Solubilization decreased the concentrations of Mg2+ required for half-maximal velocity and for saturation. Concentrations of Mn2+ required for saturation and for half-maximal velocity of particulate preparations was much lower than for Mg2+ and these values were not markedly reduced by solubilization. Particulate and soluble preparations were similarly stimulated by NaF and GPP(NH)P. Activation of the heart and skeletal muscle enzyme by NaF and GPP(NH)P greatly reduced the Mg2+ requirement; this was seen with both particulate and solubilized preparations. It is suggested that solubilization removes Mg2+ action at a regulatory site; MgATP and MnATP are both effective at the catalytic site, the latter producing higher Vmax.

Contraction-induced increase inV maxof palmitate uptake and oxidation in perfused skeletal muscle

1998 ◽  
Vol 84 (5) ◽  
pp. 1788-1794 ◽  
Author(s):  
Lorraine P. Turcotte ◽  
Carsten Petry ◽  
Bente Kiens ◽  
Erik A. Richter
Keyword(s):  
Skeletal Muscle ◽  
Substrate Concentration ◽  
Muscle Contractions ◽  
Maximal Velocity ◽  
Perfusate Flow ◽  
Palmitate Uptake ◽  
Kinetics Of Uptake ◽  
Kinetics Of ◽  
Lcfa Uptake ◽  
Menten Constant

To evaluate the effects of contractions on the kinetics of uptake and oxidation of palmitate in a physiological muscle preparation, rat hindquarters were perfused with glucose (6 mmol/l), albumin-bound [1-14C]palmitate, and varying amounts of albumin-bound palmitate (200–2,200 μmol/l) at rest and during muscle contractions. When plotted against the unbound palmitate concentration, palmitate uptake and oxidation displayed simple Michaelis-Menten kinetics with estimated maximal velocity ( V max) and Michaelis-Menten constant ( K m) values of 42.8 ± 3.8 (SE) nmol ⋅ min−1 ⋅ g−1and 13.4 ± 3.4 nmol/l for palmitate uptake and 3.8 ± 0.4 nmol ⋅ min−1 ⋅ g−1and 8.1 ± 2.9 nmol/l for palmitate oxidation, respectively, at rest. Whereas muscle contractions increased the V maxfor both palmitate uptake and oxidation to 91.6 ± 10.1 and 16.5 ± 2.3 nmol ⋅ min−1 ⋅ g−1, respectively, the K m remained unchanged. V maxand K m estimates obtained from Hanes-Woolf plots (substrate concentration/velocity vs. substrate concentration) were not significantly different. In the resting perfused hindquarter, an increase in palmitate delivery from 31.9 ± 0.9 to 48.7 ± 1.2 μmol ⋅ g−1 ⋅ h−1by increasing perfusate flow was associated with a decrease in the fractional uptake of palmitate so that the rates of uptake and oxidation of palmitate remained unchanged. It is concluded that the rates of uptake and oxidation of long-chain fatty acids (LCFA) saturate with an increase in the concentration of unbound LCFA in perfused skeletal muscle and that muscle contractions, but not an increase in plasma flow, increase the V maxfor LCFA uptake and oxidation. The data are consistent with the notion that uptake of LCFA in muscle may be mediated in part by a transport system.

Phosphorylation of myosin in permeabilized mammalian cardiac and skeletal muscle cells

1986 ◽  
Vol 250 (4) ◽  
pp. C657-C660 ◽  
Author(s):  
H. L. Sweeney ◽  
J. T. Stull
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Skeletal Muscles ◽  
Myosin Light Chain ◽  
Muscle Cells ◽  
Ventricular Muscle ◽  
Myosin Phosphorylation ◽  
Maximal Activation

The effect of myosin phosphorylation on tension production at less than 50% maximal activation by Ca2+ was examined in rabbit psoas and ventricular muscle. For psoas fibers, tension was determined at pCa 6.0, 5.8, 5.6, 5.5, and 5.4. Myosin light chain kinase (0.15 microM) and calmodulin (2 microM) were added, and the fibers were incubated at pCa 5.4, which resulted in an increase in light chain phosphorylation (P-light chain) from 5-10 to 60-75%. After 5 min, the sequence of pCa activations was repeated. An identical protocol was followed for cardiac muscle, except the activation solutions were pCa 6.2, 6.0, 5.9, 5.8, and 5.6. Phosphorylation of P-light chain increased tension in both permeabilized cardiac and skeletal muscle fibers. The effect manifested itself as a leftward shift in the pCa-tension relationship at levels below 50% maximal activation, with a decrease in the slope of the pCa-tension relationship. These results indicate that P-light chain phosphorylation affects actin-myosin interactions in cardiac and skeletal muscles at submaximal levels of Ca2+ activation

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