Pharmacological Investigations of Excitation‐Contraction Coupling

Caputo, Carlo

doi:10.1002/cphy.cp100114

Cited by 12 publications

(15 citation statements)

References 249 publications

(376 reference statements)

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“…Furthermore, the potentiation of caffeine contractures in Na+-free solutions could also be explained on a similar basis. This compound favours calcium release by SR (Kovfics & Szfics, 1983;Delay et al, 1986;Klein et al, 1990), and although its mechanism of action has not been clearly established yet (see Caputo, 1983), caffeine shifts the relation between rate of calcium release and calcium ion concentration to a lower concentration range (see Endo, 1985).…”

Section: Sodium Ions and Contractionmentioning

confidence: 99%

“…The ionic composition of the extracellular medium is known to affect the release of Ca 2+ by the sarcoplasmic reticulum (SR) and tension development in skeletal muscle (see Caputo, 1983 for a review). For example, when extracellular Ca 2 § ions are reduced to very low levels, K + contractures become shorter (L6ttgau & Spiecker, 1979) and Ca 2+ release during prolonged depolarizations decreases (Brum et al, 1988).…”

Section: Introductionmentioning

confidence: 99%

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Effect of sodium deprivation on contraction and charge movement in frog skeletal muscle fibres

García¹,

Díaz

Godı́nez

et al. 1992

J Muscle Res Cell Motil

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Measurements of isometric tension were performed in single twitch skeletal muscle fibres and the effect of extracellular Na+ removal on contraction was investigated. Na+ withdrawal brought about an increase in the amplitude of K+ contractures and their time course became faster. The potentiation of K+ contractures depended strongly on extracellular Ca2+ and developed slowly following an exponential time course with a time constant of approximately 8 min. Removal of extracellular Na+ greatly increased the amplitude of caffeine contractures and lowered its threshold: caffeine (0.5 mM) had no effect on resting tension in Ringer's but produced contractures in Na(+)-free solutions. Intramembrane charge movement (charge 1) was monitored in contracting voltage-clamped segments of frog skeletal muscle fibres using the triple-Vaseline-gap technique. Movement of charge 1 did not depend on the presence of extracellular Na+. However, the mechanical threshold decreased by approximately 10 mV at several pulse durations and the charge which produced just detectable contractions decreased by approximately 5 nC microF-1 in the absence of extracellular Na+. Intracellular heparin (40 mg ml-1) increased the mechanical threshold by approximately 20 mV without affecting the movement of charge 1. The effect of Na(+)-free solutions on the mechanical threshold was additive to that of heparin. It is concluded that the effects of Na(+)-withdrawal on contraction take place at a location beyond the voltage sensor of excitation-contraction coupling.

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Section: Sodium Ions and Contractionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of sodium deprivation on contraction and charge movement in frog skeletal muscle fibres

García¹,

Díaz

Godı́nez

et al. 1992

J Muscle Res Cell Motil

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“…There is general agreement that active mechanical tension in skeletal muskle fibres of the frog is evoked by release of Ca 2 + from the sarcoplasmic reticulum (for recent literature see Fabiato and Fabiato 1977;Caputo 1983), and the basic mechanisms of contractile activation are thought to be identical in twitch and slow fibres (Gilly and Hui 1980a, b). Important differences between the two types of muscle fibre exist, however, in their ability to maintain tension (Kuffier and Vaughan Williams 1953;Liittgau 1963).…”

Section: Introductionmentioning

confidence: 99%

The effect of D600 on potassium contractures of slow muscle fibres ofRana temporaria

1988

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(1) The effect of 30 microM D600 on the amplitude and time course of isometric contractures was studied in single slow fibres of Rana temporaria. (2) D600 only slightly reduced the amplitude of contractures evoked with 30 or 95 mM K-Ringer's. Maintenance of tension was strongly impaired by D600 only during exposure to 95 mM K. The caffeine contracture was not affected. (3) Addition of 10 mM Ca2+ or other divalent cations to the medium strongly counteracted the effect of D600 on maintained tension. The order of efficiency was Ca2+ = Ni2+ greater than Co2+ greater than Mn2+ much greater than Mg2+. (4) During 2 min exposure to 95 mM K-Ringer's the slow fibres inactivated to a variable degree; recovery from inactivation in normal Ringer's proceeded with a half time of the order of 1 min, while in the presence of D600 recovery was prolonged 3.3 to 27 times. (5) It is concluded that the effect of D600 on the contractile behaviour of slow fibres from Rana temporaria is predominantly due to a prolongation of the inactivated state. It is suggested that D600 binds to a site at the outer membrane surface which also binds divalent cations and determines the degree of contractile inactivation during exposure to potassium. Blocking of Ca2+ channels is unlikely to be the mechanism of this D600-effect.

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“…Since the work of Frank (1962) on whole frog muscle it is known that divalent cations are able to replace Ca 2+ in its effect on contractile force (for literature see also Caputo, 1983). In a more recent the Ca > concentration remained constant at 1.8 mmol/liter, but 18 sec after beginning (arrow) D600 (30/xmol/liter) was added to the medium.…”

Section: Discussionmentioning

confidence: 99%

Competitive action of divalent cations and D600 in frog slow muscle fibers

Koehler

Schmidt

1989

J. Membrain Biol.

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Single, slow muscle fibers from Rana temporaria were equilibrated in normal Ringer's. 95 mmol/liter K(+)-solution containing various concentrations of Ca2+, Ni2+, Mn2+ or Mg2+ was applied, and the ensuing contractures were recorded isometrically. While peak tension (Fmax) was little affected, maintained tension (measured 1 min after onset of contracture) strongly depended on the concentration and species of divalent cations. Tension was maintained at its peak value in the presence of all species of divalent cations provided their concentrations were adequately increased. Dose-response curves were hyperbolic; Lineweaver-Burk plots revealed straight lines with different slopes intersecting near 1/Fmax, and indicating the following order of efficiency: Ni2+ greater than Ca2+ greater than Mn2+ much greater than Mg2+. Hill plots for these cations resulted in straight lines with slopes near 1. Qualitatively similar relationships were obtained with contracture solutions containing D600 (3-12 mumol/liter). However, under these conditions higher concentrations of Ca2+ or Ni2+ were required in order to fully maintain tension. After a step concentration change in the medium during contracture, the effects of Ca2+ or D600 were detectable only after a delay of 9 and 18 sec, respectively. It is concluded that divalent cations and D600 compete for the same binding site according to a 1:1 reaction. This site is presumably located inside the transverse tubular system and controls inactivation of the contractile force.

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Pharmacological Investigations of Excitation‐Contraction Coupling

Abstract: The sections in this article are: Excitation‐Contraction Coupling Phenomena Active State Regulation of Calcium Release Mechanically Effective Period Contractile Threshold Potassium Contracture Tension Development With Voltage Clamp … Show more

Cited by 12 publications

References 249 publications

Effect of sodium deprivation on contraction and charge movement in frog skeletal muscle fibres

Effect of sodium deprivation on contraction and charge movement in frog skeletal muscle fibres

The effect of D600 on potassium contractures of slow muscle fibres ofRana temporaria

Competitive action of divalent cations and D600 in frog slow muscle fibers

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