Enhancement (by ATP, insulin, and lack of divalent cations) of ouabain inhibition of cation transport and ouabain binding in frog skeletal muscle; effect of insulin and ouabain on sarcolemmal (Na + K)MgATPase

1977 ◽  
Vol 55 (1) ◽  
pp. 21-33 ◽  
Author(s):  
J. F. Manery ◽  
E. E. Dryden ◽  
J. S. Still ◽  
G. Madapallimattam
Keyword(s):  
Skeletal Muscle ◽  
Extracellular Space ◽  
Divalent Cations ◽  
Membrane Surface ◽  
Cation Transport ◽  
Frog Skeletal Muscle ◽  
Ouabain Binding ◽  
Maximum Inhibition ◽  
Ouabain Inhibition ◽  
External K

Using small, intact frog muscles, the basic properties of Na+ and K+ transport were shown to resemble those of the (Na+ + K+) Mg2+ATPase (EC 3.6.1.3) isolated from skeletal muscle, (a) External K+ is essential for Na+ exit and K+ entry after the muscles are Na+-loaded and K+-depleted; (b) the ouabain concentration causing maximum inhibition of recovery is the same for transport as for the inhibition of the isolated enzyme. Ouabain causes a decrease in the sorbitol space and causes muscle fibre swelling. Absence of Ca2+ and Mg2+ inhibits recovery of normal Na+ and K+ concentrations and increases the sorbitol space. Insulin stimulates K+ uptake and Na+ loss in intact muscles but has no effect on the isolated sarcolemmal (Na+ + K+) Mg2+ATPase. Absence of divalent cations, addition of external ATP and of insulin enhance the ouabain inhibition of recovery.Bound ouabain was measured using [3H]ouabain and [14C]sorbitol (to measure the extracellular space). The process of binding was slowly reversible and was saturable within a range of ouabain concentrations from 1.48 × 10−7 to 5.96 × 10−7 M. From the nonexchangeable ouabain bound, the density of glycoside receptors was estimated to be 650 molecules per square micrometre of membrane surface. The absence of divalent cations, addition of external ATP and of insulin significantly enhanced the amount of ouabain bound. Substitution of Na+ and K+ by choline greatly reduced the bound ouabain.

Some effects of organic anions on excitability and excitation–contraction coupling in frog skeletal muscle

1977 ◽  
Vol 55 (3) ◽  
pp. 700-708 ◽  
Author(s):  
J. G. Foulks ◽  
Florence A. Perry
Keyword(s):  
Skeletal Muscle ◽  
Divalent Cations ◽  
Membrane Surface ◽  
Organic Anions ◽  
Polar Group ◽  
Frog Skeletal Muscle ◽  
Excitation Contraction Coupling ◽  
Partial Restoration ◽  
Contraction Coupling ◽  
Contractile Performance

When substituted for external chloride, organic anions differed markedly from one another in the extent to which they produced hyperexcitability and in the direction and intensity of their effects on twitch tension in frog skeletal muscle. All of the anions studied reduced the threshold [K]0 for K contractures and most enhanced twitch tension. Among carboxylate anions, increasing the size of the attached apolar hydrocarbon chain led to decreased hyperexcitability and to reduction in the amplitude of twitches and maximum K-contractures, butyrate being the most effective depressant of these responses. Sulfonate anions produced much less conspicuous changes in contractile performance. With γ-hydroxybutyrate, the introduction of a polar group on the hydrocarbon terminus resulted in twitch enhancement and partial restoration of maximum K-contracture tension. The depressant effect of butyrate on K contractures was partially overcome by a fivefold increase in the external concentration of calcium but twitches were unaffected. Perchlorate (12 mM) effectively antagonized the depressant actions of butyrate on twitches as well as K contractures. Most of the effects of these anions were prompt in onset. Impairment of contractile performance by butyrate was not accompanied by appreciable changes in membrane resting or action potentials or in the relation between [K]0 and membrane potential, and took place in spite of reduction in K-contracture threshold. Such effects must result from alteration in excitation–contraction coupling, possibly by interference with the binding of divalent cations to the membrane surface.

The influence of pH on the effects of organic anions in frog skeletal muscle

1977 ◽  
Vol 55 (5) ◽  
pp. 1122-1134 ◽  
Author(s):  
J. G. Foulks ◽  
Florence A. Perry ◽  
P. Tsang
Keyword(s):  
Skeletal Muscle ◽  
Divalent Cations ◽  
Organic Anions ◽  
Frog Skeletal Muscle ◽  
Depressant Effect ◽  
Contractile Responses ◽  
Neutral Ph ◽  
Acid Ph ◽  
Depressant Action ◽  
Carboxylate Anions

The depressant effect of acidity on twitches and K contractures in frog skeletal muscle was greatly accentuated in the presence of organic anions, particularly anions such as butyrate, which also reduced these responses at neutral pH. Conversely, alkaline pH antagonized the depression of contractile responses by butyrate. Most of the effects of acid pH were rapid in onset and were accomplished without any change in membrane resting or action potentials, although depolarization developed in the presence of carboxylate anions when pH was reduced below 6.0. Simultaneous variation in pH and butyrate concentration showed that the undissociated acid exerted a prominent depressant effect only when its concentration reached 1–10 mM, and that the marked depressant action of butyrate at neutral pH was produced primarily by the dissociated anion. Similar experiments showed that the dissociated anion also was largely responsible for the enhanced depolarizing effect of acidity in media containing carboxylates. Acid-induced depolarization was not facilitated in media containing methane sulfonate, but in spite of its low pKa, this anion also increased the sensitivity of contractile responses to the depressant effects of acidity. Hence, the accentuation of the effects of organic anions by acid pH must be exerted on the sequence of membrane events which link excitation and contraction. The effect of acidity was greater when longer apolar hydrocarbon chains were attached to the anionic group for both the carboxylate and the sulfonate series of ions. These depressant effects may be produced by interference with the membrane-stabilizing actions of divalent cations, and may involve increased membrane fluidity.

scholarly journals Strophanthidin-sensitive sodium fluxes in metabolically poisoned frog skeletal muscle.

1976 ◽  
Vol 68 (4) ◽  
pp. 405-420 ◽  
Author(s):  
B G Kennedy ◽  
P De Weer
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Human Erythrocyte ◽  
Sodium Pump ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Frog Skeletal Muscle ◽  
Na Efflux ◽  
Unidirectional Fluxes ◽  
External K

Strophanthidin-sensitive and insensitive unidirectional fluxes of Na were measured in fog sartorius muscles whose internal Na levels were elevated by overnight storage in the cold. ATP levels were lowered, and ADP levels raised, by metabolic poisoning with either 2,4-dinitrofluorobenzene or iodoacetamide. Strophanthidin-sensitive Na efflux and influx both increased after poisoning, while strophanthidin-insensitives fluxes did not. The increase in efflux did not require the presence of external K but was greatly attenuated when Li replaced Na as the major external cation. Membrane potential was not markedly altered by 2,4-dinitrofluorobenzene. These observations indicate that the sodium pump of frog skeletal muscle resembles that of squid giant axon and human erythrocyte in its ability to catalyze Na-Na exchange to an extent determined by intracellular ATP/ADP levels.

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.

Fusion of Sarcoplasmic Reticulum with Ruthenium Red

1975 ◽  
Vol 33 ◽  
pp. 500-501
Author(s):  
N. Wallace ◽  
J.R. Sommer
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Membrane Fusion ◽  
Extracellular Space ◽  
Ruthenium Red ◽  
Frog Skeletal Muscle ◽  
Definition Of ◽  
Terminal Cisternae ◽  
Structural Definition

Howell recently reported the effect of Ruthenium Red (RR) on the sarcoplasmic reticulum (SR) of frog skeletal muscle after long exposures to that dye. Howell observed staining of the junctional granules within the junctional SR (terminal cisternae), and fusion of the so-called intermediate cisternae that are intercalated between junctional and free SR. This is an important observation because it may provide, first, needed additional evidence for a structural definition of the so-called intermediate cisterna, and second, the fusion of the intermediate cisternae under these circumstances suggests that they might have properties that are different from, or in addition to those of the junctional and free SR, respectively. For example, membrane fusion in that region might conceivably occur in vivo under certain circumstances in which case a large proportion of the SR might become separated, electrically, from the junctional SR. As a result, at least temporary openings of the junctional SR to the extracellular space remain a possibility even during depolarization.

Restoration of the Ability of Frog Skeletal Muscle to Develop Potassium Contractures in Calcium-Deficient Media

1973 ◽  
Vol 51 (5) ◽  
pp. 335-343 ◽  
Author(s):  
J. G. Foulks ◽  
J. A. D. Miller ◽  
Florence A. Perry
Keyword(s):  
Skeletal Muscle ◽  
Contractile Function ◽  
Divalent Cations ◽  
Frog Skeletal Muscle ◽  
Free Media ◽  
Dependent Processes

A number of agents were tested for their ability to restore potassium (K) contractures in calcium-free media. Effective agents included caffeine, chloroform, more polar permeant anions (e.g. nitrate and perchlorate) in place of external chloride, as well as divalent cations, e.g. Mg2+. The presence of sufficient EGTA to preclude significant increases in [Ca]0 did not affect the extent of K contracture restoration produced by these agents. The loss of K contracture capacity in calcium-free media, and its restoration by effective agents, appear to be related to the disproportionate effect of these procedures on the relation between log [K]0 and the potential-dependent processes which regulate contractile function.

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