Active state prolongation associated with depolarization in frog's skeletal muscle

Clinch, N. F.

doi:10.1139/y68-124

Cited by 3 publications

(2 citation statements)

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“…Maintained, subthreshold depolarization of a muscle is known to be associated with a prolongation of the active state. This effect was not related to an increase in the action potential "area" (Clinch 1968). In several previous studies, hypertonic solutions were reported to cause a depolarization of the muscle (Tigyi andShih-Fang 1962, Gordon andGodt 1970), but the measurements were usually performed in solutions of very high tonicity, 3-4 R. The present experiments did not show any marked changes of the membrane potential in 1.44-1.67 R. In some fibres there was a slight depolarization, but more often a hyperpolarization of 3-8 mV was seen.…”

Section: Discussionmentioning

confidence: 74%

The Effect of Hypertonicity on the Time Course of the Active State in Single Skeletal Muscle Fibres of the Frog

Andersson

1973

Acta Physiologica Scandinavica

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The time course of the active state was investigated in single skeletal frog muscle fibres in normal Ringer's solution and in Ringer's solution made hypertonic (1.44–1.67 R) by addition of sucrose. During a single, isometric twitch the plateau phase of the active state was abbreviated in hypertonic solution. During repetitive stimulation there was a progressive increase in the duration of the active state and a slowing of the rate of decay of the activity in the hypertonic medium. The resting membrane potential was insignificantly affected by the hypertonic solutions used. There was a slight decrease in overshoot and also a diminution in the rate of rise and rate of decay of the action potential. As a possible explanation of the results, it is suggested that in a hypertonic medium there is a diminished release of calcium in response to a stimulus. This leads to a shortening of the plateau phase of the active state during a single twitch. Because of a reduced rate of re‐uptake of calcium by the sarcoplasmic reticulum, the duration of the active state is prolonged and the decay of activity slowed during repetitive stimulation.

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Section: Discussionmentioning

confidence: 74%

The Effect of Hypertonicity on the Time Course of the Active State in Single Skeletal Muscle Fibres of the Frog

Andersson

1973

Acta Physiologica Scandinavica

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“…From the argument offered above regarding the total absence of the positive inotropic effect when the potassium level is raised only in the long segment, it may be regarded as unlikely that membrane depolarization during the resting state (i.e., diastole) is involved in the mechanism of the positive inotropic effect. This is in contrast to the effect of potassium-induced depolarization in prolonging the active state in skeletal muscle (Clinch, 1968;Chapman, 1969). Additional evidence on this point has been provided by Beeler and Reuter (1970 b), who found that small depolarizations (e.g., 8 my, as in Fig.…”

Section: Discussionmentioning

confidence: 78%

Positive and Negative Inotropic Effects of Elevated Extracellular Potassium Level on Mammalian Ventricular Muscle

Kavaler

Hyman

Lefkowitz

1972

The Journal of General Physiology

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The effect of moderate elevation in extracellular potassium concentration (up to 12 mm) on contraction of cat ventricular muscle was examined. Isometric force development was recorded from eight excised trabeculae and from six coronary-perfused in situ papillary muscle preparations. Contraction in the steady state was variably affected, sometimes decreasing monotonically, sometimes remaining unchanged, with increasing potassium level. In 11 of these 14 preparations, the steady state was preceded by a transient period in which the contraction was augmented. In addition, eight excised trabeculae were used in an experimental arrangement designed to distinguish between inotropic effects caused by potassium-induced alterations in the action potential and other, more direct, effects of this ion on contraction. The negative inotropic effect is attributable to a potassium-induced reduction in the amplitude and/or duration of the action potential plateau. The positive inotropic effect was found in experimental arrangements where effects of the potassium-rich medium on action potential time-course were effectively "buffered." The positive inotropic effect thus depends on the presence of the elevated potassium concentration and can occur independently of effects on the action potential time-course.

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Depressing effects of calcium antagonists on oxygen consumption in isolated skeletal muscle during potassium depolarization

Barnes

1988

Can. J. Physiol. Pharmacol.

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The effects of two Ca2+-antagonizing drugs, dantrolene sodium (DAN) and TMB-8, on subcontracture, K+-induced increased oxygen consumption were studied in isolated frog sartorius muscles. Incubation in Ringer's solution +18 mM KCl caused a marked increase in averaged resting oxygen uptake (52.8 +/- 4.1 to 278.2 +/- 20.0 mm3.g-1.h-1). Incubation in Ringer's +18 mM KCl containing either 0.116 mM TMB-8 or 0.035 mM DAN resulted in a significant reduction in the averaged metabolic response (264.4 +/- 30.8 (control) vs. 142.3 +/- 19.0 (TMB-8) vs. 72.2 +/- 3.4 (DAN]. The results suggest that the enhanced metabolic rate observed upon elevating extracellular [K+] to just below contracture levels is due to increased intracellular Ca2+ release.

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Active state prolongation associated with depolarization in frog's skeletal muscle

Cited by 3 publications

References 0 publications

The Effect of Hypertonicity on the Time Course of the Active State in Single Skeletal Muscle Fibres of the Frog

The Effect of Hypertonicity on the Time Course of the Active State in Single Skeletal Muscle Fibres of the Frog

Positive and Negative Inotropic Effects of Elevated Extracellular Potassium Level on Mammalian Ventricular Muscle

Depressing effects of calcium antagonists on oxygen consumption in isolated skeletal muscle during potassium depolarization

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