The dynamics of the effect of potassium on frog's muscle

The most widely accepted theory of the restirng potential of muscle is that the electrical potential difference between the inside and outside of a muscle fibre arises from the concentration gradients of the potassium and chloride ions. If we follow Boyle & Conway (1941), the membrane is assumed to be permeable to K and Cl but to be impermeable or sparingly permeable to other ions. Since K is more concentrated inside and Cl is more concentrated outside, the interior of the fibre should be electrically negative to the external solution. If K and Cl are distributed passively, the concentration ratios and the membrane potential under equilibrium conditions ought to conform to the relationwhere [ ]O and [ ]i indicate concentrations outside and inside the fibre, V is the internal potential, F is Faraday's constant, R is the gas constant and T is the absolute temperature. When the external potassium concentration is less than 10 mm agreement with equation (1) is not perfect, but at higher concentrations the relation seems to hold with considerable accuracy (Adrian, 1956;Conway, 1957). However, it is only possible to calculate the membrane potential by equation (1) when the concentrations of K and Cl inside the fibre have come into equilibrium with those in the external solution. In order to deal with other situations one must know the relative conductances or permeabilities of the two ions. Information on this point can be obtained by measuring the effect on membrane potential of sudden changes in the concentrations of K or Cl. Such experiments are difficult to interpret unless the effect of changing the external solution can be determined in a time which is so short that there is no alteration in the internal concentration of Cl or K. The present observations were carried out with single muscle fibres, with an

show abstract

“…An asymmetry of the kind shown in Fig. 7 has been seen in experiments with whole muscle by Sandow & Mandel (1951) and Csapo & Wilkie (1956).…”

Section: Methodsmentioning

confidence: 76%

The influence of potassium and chloride ions on the membrane potential of single muscle fibres

Hodgkin¹,

Horowicz²

1959

The Journal of Physiology

1,414

929

View full text Add to dashboard Cite

show abstract

“…This is due to loss of potassium from the interspaces by exchange across the cell membrane, so that the amount transferred in the interspaces in unit time is diminished. Csapo & Wilkie (1956) show that De is given approximately by aD' where a is the fraction by volume of the interspaces. Now a for diaphragm is 0-28 (Creese, 1954) and this argument leads in the present experiments to a value of 1P5 x 10-6 cm2/sec for the effective diffusion coefficient for net transport of potassium.…”

Section: Discussionmentioning

confidence: 95%

Potassium movements in contracting diaphragm muscle

Creese¹,

Hashish²,

Scholes³

1958

The Journal of Physiology

View full text Add to dashboard Cite

“…In the experiment shown in Fig 1, some potassium would enter the fibres as well as the interspaces. It has been shown by Csapo & Wilkie (1956) that, under such conditions, the effective diffusion coefficient for potassium accumulation in the interspaces would be aD', where a is the fraction by volume of the interspaces. This fraction is 0.28 for diaphragm muscle (Creese, 1954).…”

Section: Discussionmentioning

confidence: 99%

“…Thus the unblocking action of potassium ions proceeds more rapidly in the case of thin muscles than can be accounted for by the simple theory. Csapo & Wilkie (1956) studied the rate at which high concentrations of potassium ions produced reversible inexcitability in frog muscle, and concluded that interfibre diffusion was responsible. In their studies the concentration of potassium in the interspaces had to reach a critical value (9 mM) before a fibre was affected.…”

Section: Discussionmentioning

confidence: 99%

Rate of Antagonism of Tubocurarin by Potassium Ions

Creese

Taylor

Tilton

1961

British Journal of Pharmacology and Chemotherapy

View full text Add to dashboard Cite

The rate at which potassium ions antagonized the neuromuscular block produced by tubocurarine has been examined in isolated rat diaphragm muscle preparations. The half-time was dependent on the thickness of the muscle. In thick muscles (550 to 650 p) the rate of action could be largely accounted for by the time which the potassium took to diffuse through the interstitial fluid to produce an increase in concentration in the immediate environment of the muscle fibre.It is well known that addition of potassium antagonizes the blocking action of tubocurarine in skeletal muscle (Wilson & Wright, 1936;Quilliam & Taylor, 1947). When this is studied in isolated muscle, the process takes a measurable time for completion, and it was of interest to determine how far diffusion of potassium through the interstitial spaces to its site of action could account for the time relations. METHODSThe solution bathing the diaphragm was similar to that used by Creese (1954) except that the potassium content was reduced to 1.5 mm. The fluid was bubbled with a mixture of 5% carbon dioxide and 95% oxygen, and the temperature of the bath was maintained at 380 C.The left hemi-diaphragm from an albino rat weighing 100 to 150 g was removed, attached to a holder and immersed in the solution in such a manner that single maximal shocks could be delivered alternately to the nerve and muscle, using the procedure described by Holmes, Jenden & Taylor (1951) except that condenser shocks of 0.02 /F were used for the nerve and 2 /OF for the muscle. The responses were recorded on smoked paper using a spring-loaded lever. Stimulation was continued throughout the experiments, and the magnitude of the responses obtained by direct and indirect stimulation was very similar. As direct stimulation was almost unaffected by tubocurarine, an estimate of the degree of block could be made at any time during the experiment.The muscle was later removed from the bath, outlined on squared paper and weighed. The thickness was calculated, taking the specific gravity as 1.055 (Creese, 1954) and expressing the result to the nearest S a. RESULTSThe height of contraction of the muscle after immersion in the solution containing 1.5 mm potassium showed an initial decline. The solution was changed repeatedly until the height of contraction became steady, usually after 2 hr.

show abstract

The dynamics of the effect of potassium on frog's muscle

Cited by 23 publications

References 23 publications

The influence of potassium and chloride ions on the membrane potential of single muscle fibres

The influence of potassium and chloride ions on the membrane potential of single muscle fibres

Potassium movements in contracting diaphragm muscle

Rate of Antagonism of Tubocurarin by Potassium Ions

Contact Info

Product

Resources

About