Effects of ‘Edta’ on the Membrane Potential and Tension of Ventricular Muscle of the Rabbit

Goto, Masayosi; Abe, Yoshiharu

doi:10.2170/jjphysiol.14.135

Cited by 19 publications

(4 citation statements)

References 20 publications

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“…When 2-5 HIM disodium ethylenediamine tetraacetate (EDTA) was added to one compartment of the muscle chamber, the action potential duration recorded in that compartment was prolonged and the action potential spike diminished in a few minutes (Fig. 2), as has been reported by others (7,8). In the Purkinje fiber-papillary muscle preparation, EDTA was added to the compartment containing the Purkinje fiber.…”

Section: Resultssupporting

confidence: 54%

Abnormal Automaticity in Canine Purkinje Fibers Focally Subjected to Low External Concentrations of Calcium

Sano

Sawanobori

1972

Circulation Research

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The false tendon was isolated from the dog heart and mounted under a partition plate in the center of a chamber which was filled with Tyrode's solution. Two microelectrodes were positioned closely on either side of the plate and inserted into the false tendon. The partition did not alter repolarization of the action potential in normal Tyrode's solution. When EDTA was added to one side of the preparation, a low-plateau potential appeared after repolarization on the other side, which contained normal Tyrone's solution. This change occurred concurrently with a prolongation of the action potential in the calcium-free Tyrode's solution. The low-plateau potential was a reflection of the electrotonic potential from the nearby cells whose action potentials were prolonged. Repetitive firing of the action potential was frequently observed when abrupt differences in repolarization were recorded at close interelectrode distances. These results suggest that differences in repolarization of closely apposed cells can initiate arrhythmias.KEY WORDS coupled extrasystoles low-plateau potential arrhythmia due to repolarization difference focal reexcitation repetitive firing 158

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Section: Resultssupporting

confidence: 54%

Abnormal Automaticity in Canine Purkinje Fibers Focally Subjected to Low External Concentrations of Calcium

Sano

Sawanobori

1972

Circulation Research

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“…Similar action potentials produced in low or zero calcium with a chelator has been also observed in cardiac muscle fibers (CHANG and SCHMIDT, 1960;GOTO and ABE, 1964;GARNIER et al, 1969;TRITTHART et al, 1973;MILLER and MORCHEN, 1978) and in smooth muscle fibers (PROSSER et al, 1977).…”

supporting

confidence: 73%

“…In heart muscle fibers, the duration of an action potential observed in zero calcium with a chelator was dependent on the extracellular sodium concentrations; the increase in sodium concentration prolonged the plateau phase and the decrease in it acts contrarily (GOTO and ABE, 1964;GARNIER et a!., 1969). GARNIER et al (1969) reported that the existence of a slow inward sodium current, which was blocked by the action of magnesium, was responsible for long duration of response in frog atrial muscle fibers.…”

Section: Discussionmentioning

confidence: 99%

Prolonged action potential of frog skeletal muscle membrane in Ca-free EGTA solution.

Minota

Koketsu

1983

Jpn.J.Physiol

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The membrane of isolated frog skeletal muscle fibers with or without T-system is depolarized to about -30 mV in a Ca-free solution containing 2 mM EGTA. Under such a condition, the action potential can be produced by a cathodal pulse when the membrane is previously hyperpolarized to -70--100 mV by a conditioning anodal current. The action potential consists of two different potential components, namely a spike potential and a following slow depolarizing response forming a plateau phase (plateau potential). The membrane conductance during the plateau potential is increased. Both spike and plateau potentials are abolished in the absence of NaCI. TTX blocks a spike potential without affecting a plateau potential, whereas Mn and D-600 act contrarily. The i-v relation shows an anomalous rectification in Na-free solution, suggesting that the K conductance during the plateau phase is decreased. It is suggested that spike and plateau potentials are produced by a movement of sodium ions through sodium and calcium channels of the membrane, respectively.

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“…8 (A)). It is suspected that in the presence of EGTA, not only the membrane Ca but also the Ca in the interior of the cell membrane are depleted (GOTO and ABE, 1964). From these experimental results it might be assumed that the Ca for activating the tonic contraction of the delayed effect is released from the Ca binding sites in the cell membrane.…”

Section: Discussionmentioning

confidence: 96%

The Rapid Cooling Contracture of Toad Cardiac Muscles

Sakai

Kurihara

1974

Jpn.J.Physiol

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Summary The effect of rapid cooling on the mechanical activities of the cardiac muscles of the Japanese toad was examined. 1. The mechanical responses produced by rapid cooling (230•Ž) in both auricular and ventricular muscle preparations were composed of an immediate effect (phasic contraction) and a delayed effect (tonic contraction). The immediate effect was blocked by TTX, but the delayed effect was not affected by TTX and Mn. 2. The tonic contraction of the delayed effect produced by rapid cooling was potentiated in Na-deficient Ringer solution in which an equivalent amount of NaCl was substituted for Tris-Cl. The relationship between the relative tension of the delayed effect produced by rapid cooling and the ratio of [Ca2+]/[Na+]2 showed an S-shaped curve. 3. Generation of tension development of the delayed effect produced by rapid cooling was obviously dependent upon the extracellular Ca concentrations. There was an S-shaped relationship between the relative tension of the delayed effect and pCa in the extracellular medium. 4. In the test solution containing Ca less than pCa 8.0, no tension development of the delayed effect was observed. However, the rapid cooling contracture was strongly elicited by application of caffeine (caffeine-RCC). 5. The caffeine-RCC was also observed in the presence of 100 mM KCl. 6. From the results of the present study, it was considered that, even though the Ca influx was abolished, the contraction of the cardiac muscle could be produced by another mechanism, probably due to increase of myoplasmic Ca released by rapid cooling from the cell membrane itself and the sarcoplasmic reticulum. Since 1960, SAKAI et al. (1960, 1965 have studied the effect of rapid cooling on the mechanical responses of normal and T-tubules distrupted skeletal muscles in the presence of a subthreshold concentration of caffeine, and concluded

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Effects of ‘Edta’ on the Membrane Potential and Tension of Ventricular Muscle of the Rabbit

Cited by 19 publications

References 20 publications

Abnormal Automaticity in Canine Purkinje Fibers Focally Subjected to Low External Concentrations of Calcium

Abnormal Automaticity in Canine Purkinje Fibers Focally Subjected to Low External Concentrations of Calcium

Prolonged action potential of frog skeletal muscle membrane in Ca-free EGTA solution.

The Rapid Cooling Contracture of Toad Cardiac Muscles

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