Electrotonic Interaction between Muscle Fibers in the Rabbit Ventricle

Tille, J.

doi:10.1085/jgp.50.1.189

Cited by 27 publications

(11 citation statements)

References 9 publications

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“…Although we are not aware of a theoretical equation that can be used to calculate the voltage decrement expected in a finite multidimensional preparation, we assumed that a direct comparison of the profile of voltage decrement in HBP and SHAM preparations would at least permit us to identify a difference in those passive membrane properties that determine the pattern of current flow. To obtain a rough estimate of what a reasonable length of preparations should be for our experiments, we first determined the length constant, X, of normal rat ventricular muscle by one-dimensional cable analysis (Kamiyama and Matsuda, 1966;Tille, 1966;Sakamoto and Goto, 1970). In four ventricular muscle preparations X was 1.0 ± 0.2 mm (mean ± SD), a value similar to that reported in a previous study (Mainwood and McGuigan, 1975).…”

Section: Analysis Of Electronic Voltage Decrementsupporting

confidence: 59%

Non-uniform electrophysiological properties and electrotonic interaction in hypertrophied rat myocardium.

Keung¹,

Aronson²

1981

Circulation Research

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SUMMARY We studied the distribution and nature of the electrical changes associated with myocardial hypertrophy induced by renal hypertension in rats. Standard microelectrode techniqueB were used to study transmembrane action potentials recorded from endocardial, papillary muscle, and epicardial fibers from hypertrophied (HBP) and normal (SHAM) hearts. We also determined the effects of stimulation frequency on the action potentials recorded from these preparations. To assess whether altered intercellular electrical connections contribute to the electrophygiological changes associated with hypertrophy, we analyzed the spatial steady state voltage decrement produced by passing intracellular constant current pulses and determined the effective input resistance (R^,) of endocardial HBP and SHAM preparations. Our results show that the action potential prolongation that accompanies hypertrophy is not uniform. Thus, the entire course of repolarization is prolonged in endocardial and papillary muscle fibers, but only the latter half of repolarization is prolonged in epicardial fibers. Endocardial action potentials in general, and HBP action potentials in particular, have a distinctive steep relation between duration and stimulation frequency which may be due to a difference in the rate dependence of a membrane conductance ( RENOVASCULAR hypertension in rats produced by unilateral clipping of one renal artery imposes a gradual and chronic pressure overload on the heart. Left ventricular hypertrophy resulting from such a chronic pressure overload is associated with characteristic contractile Kammereit and Jacob, 1979; Capasso et al., 1980), ultrastructural (Wendt-Gallitelli andLoud et al., 1978;Anversa et al., 1978;Wendt-Gallitelli et al., 1979), and electrophysiological alterations (Gulch et al., 1979; Aronson, 1980).The most consistent alterations in the myocardium of rats with renal hypertension are enlargement of the myocytes and prolongation of the action potential. However, the degree of alteration in these properties appears to vary according to the region of the left ventricle studied. For example, in a morphometric study of hypertrophied left ventricles from rats with renal hypertension, Loud et al. (1978) and Anversa et al. (1978) reported a greater enlargement of epicardial cells than endocardial cells after 1-4 weeks of hypertension. In the same model, Aronson (1980) recently reported a 50% prolongation of action potential duration in hypertrophied rat papillary muscle driven at a cycle length of 1000 msec (35°C), and Gulch et al. (1979) reported a 180% increase in action potential duration in left ventricular trabeculae driven at a cycle length of 5000 msec (25°C). These results suggest that hypertrophy induced by renal hypertension may be a non-uniform process that affects endocardial, papillary muscle, and epicardial fibers to a different degree.The purpose of the present study was to characterize further the distribution and nature of the electrical changes associated with myocardial hypertrophy. This was...

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Section: Analysis Of Electronic Voltage Decrementsupporting

confidence: 59%

Non-uniform electrophysiological properties and electrotonic interaction in hypertrophied rat myocardium.

Keung¹,

Aronson²

1981

Circulation Research

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“…This means that it is difficult to define precisely the area of membrane which contributes to the measured resistive and capacitative currents. (iii) Injection of current through an intracellular micro-electrode (Tille, 1966;Tanaka & Sasaki, 1966;Sakamoto, 1969). The main limitation of this method-as it was applied by these authors-lies in the fact that three-dimensional spread of current must be considered in the large preparations used, which makes the analysis much more difficult.…”

Section: Introductionmentioning

confidence: 99%

The passive electrical properties of guinea‐pig ventricular muscle as examined with a voltage‐clamp technique.

Daut¹

1982

The Journal of Physiology

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SUMMARY1. A voltage-clamp technique was developed for stable recording of small currents in guinea-pig ventricular muscle. Small cylindrical preparations were impaled with three micro-electrodes, one for measuring the feed-back potential and two for injecting current.2. The longitudinal potential profile resulting from current injection at one point was measured. It agreed well with the theoretical predictions for a linear cable which is sealed at both ends ('healing over'), with a length constant (A) of 580+ 145 /tm.3. When the clamp current was injected symmetrically into each half of the preparation via two electronic current pumps a spatially homogeneous clamp could be achieved in preparations with a diameter of < 250 pum and a length of K 2 A.4. The membrane capacity and the membrane resistance of the preparations at the resting potential were measured with small voltage-clamp pulses. Assuming a specific membrane capacity (Cm) of 1 #sF/cm2 a specific membrane resistance (Rm) of 6-7 + 1-8 kQ cm2 was obtained in Tyrode solution containing 3 mM-K.5. The total surface area was calculated from the measured capacity of the preparation assuming a Cm of 1 ,sF/cm2. The total cellular volume was estimated from optical measurement of the external dimensions of the preparation assuming an extracellular space of 25 %. From these data the average surface/volume ratio of individual cells was calculated to be 7200 cm2/cm3. 6. From the measured electrical constants the specific resistance of the intracellular space (Ri) was calculated to be 200-250 Q cm. With small constant current pulses a membrane time constant of 6-6+ 1-3 ms was measured.

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“…Different methods have been used to determine the passive electrical properties. For instance, subthreshold current has been made to flow through one intracellular micro-electrode, and potential changes have been recorded from different intracellular sites by means of a second micro-SILVIO WEIDMANN electrode (Woodburry & Crill, 1961;Tarr & Sperelakis, 1964;van der Kloot & Dane, 1964; Berkinblit, Kovalev, Smolyaninov & Chailakhyan, 1965;Tille, 1966;Tanaka & Sasaki, 1966). Alternatively, large extracellular electrodes have been used to polarize a bundle of fibres, and the voltage distribution has been mapped out either by extracellular electrodes (Trautwein, Kuffler & Edwards, 1956), or by intracellular electrodes (Kamiyama & Matsuda, 1966;Sakamoto, 1969).…”

Section: Introductionmentioning

confidence: 99%