Background K+ current in isolated canine cardiac Purkinje myocytes

Shah, Anuradha; Cohen, Ira S.; Datyner, N B

doi:10.1016/s0006-3495(87)83241-1

Cited by 36 publications

(33 citation statements)

References 32 publications

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“…While it has been known for a long time that Purkinje fibers display two levels of RP [27], this differs significantly from ventricular muscle. Purkinje cells have reasonably strong I K1 [28] but some characteristics (the nature of the negative slope) differ from ventricle(see [29]). Before full repolarization of AP, one or two early afterdepolarizations (EADs) were sometimes observed in the Purkinje cells with slightly more positive RP in normal [K + ] o .…”

Section: Resting Potentialmentioning

confidence: 99%

The Purkinje cell; 2008 style

Dun

Boyden

2008

Journal of Molecular and Cellular Cardiology

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Cardiac Purkinje fibers, due to their unique anatomical location, cell structure and electrophysiologic characteristics, play an important role in cardiac conduction and arrhythmogenesis. Purkinje cell action potentials are longer than their ventricular counterpart, and display two levels of resting potential. Purkinje cells provide for rapid propagation of the cardiac impulse to ventricular cells and have pacemaker and triggered activity, which differs from ventricular cells. Additionally, a unique intracellular Ca 2+ release coordination has been revealed recently for the normal Purkinje cell. However, since the isolation of single Purkinje cells is difficult, particularly in small animals, research using Purkinje cells has been restricted. This review concentrates on comparison of Purkinje and ventricular cells in the morphology of the action potential, ionic channel function and molecular determinants by summarizing our present day knowledge of Purkinje cells.

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Section: Resting Potentialmentioning

confidence: 99%

The Purkinje cell; 2008 style

Dun

Boyden

2008

Journal of Molecular and Cellular Cardiology

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“…The inward rectifier current can be studied by determining the steady-state I-V relation of a cell in control conditions and following channel blockade (see Shah, Cohen & Datyner, 1988). The difference current under these conditions represents the I-V relation of iK1* In a set of experiments, we analysed the inward rectifier current in the valve cells, the results of which are shown in Fig.…”

Section: Inward Rectifier Current Ik1mentioning

confidence: 99%

Electrophysiology of single heart cells from the rabbit tricuspid valve.

Anumonwo

Delmar

Jalife

1990

The Journal of Physiology

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SUMMARY1. The electrophysiology of single myocytes isolated from the rabbit tricuspid valve was studied using the patch-clamp method (whole-cell configuration). Cell dispersion was achieved by collagenase treatment, using the Langendorff retrograde perfusion procedure.2. After isolation, and while incubating in the recovery (Kraftbriihe) solution, cells had clear striations and were mostly spindle-shaped, or rod-like (< 10 %), with length varying from 35 ,tm to over 150 ,tm, and diameter from 3 to 10 jsm.3. Upon exposure to Tyrode solution, the calcium-tolerant cells were mostly rounded with smooth surfaces and well-defined borders. The mean diameter of these cells was 15 + 5 ,um (S.D., n = 9). A smaller percentage (about 30 %) retained the original elongated shape. 4. Patch pipette recordings showed the presence of spontaneous activity in about 30% of round cells, and less frequently in elongated cells. Maximum diastolic potentials (MDPs) in the round cells averaged -82 + 6 mV, with a take-off potential of -56+3 mV (n = 9), and an average maximum upstroke velocity (Vmax) value of 6-3 + 0-6 V/s (n = 4). In quiescent cells, the mean resting potential was 69 + 12 mV (n = 43).5. Voltage clamp ramps revealed a steady-state I-V relation with a negative slope region. The mean input resistance value was 25+9 MC (n = 16) for the elongated, and 883 +481 MC (n = 8) for the round cells.6. Hyperpolarizing 5 s pulses (holding potential =-50 mV) occasionally revealed a slow, time-dependent inward current whose peak increased progressively as a function of clamp potential. The slowly activating current was sensitive to caesium (2 mM), indicating its similarity to the so-called 'pacemaker current' (iF). In alternate voltage-and current-clamp experiments, blocking of iF did not stop pacemaker activity, but there was up to a fourfold increase in pacemaker cycle length.7. In some cells, 5 s hyperpolarizing steps from a holding potential of -40 or -50 mV produced large, inwardly directed and voltage-dependent current surges that decayed rapidly with time, similar to the inactivation described for the inward rectifier current, iK1. The current was very prominent at voltages more negative than -100 mV, and its decay process was best fitted by two time constants, one fast and MS 7831 J. M. B. ANUMONWO, M. DELMAR AND J. JALIFE one slow. For example, at -150 mV the time constants were 61 and 634 ms. The inward current was blocked by barium (1 mM).8. The current inactivation process was also shown to occur at a less negative potential, at -90 mV; however, one time constant, with a value of 270 ms, was sufficient to fit the current decay process at this potential.9. Depolarizing voltage-clamp steps (200 ms duration) from a holding potential of -50 or -60 mV revealed a cobalt (2 mM)-sensitive transient inward current that peaked around 0 mV and that had a reversal potential of + 50 to + 60 mV. Longer duration (3-5 s) depolarizing pulses produced, first, the cobalt-sensitive current and then an outward current with a time course and activat...

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“…The salient features of I K1 , such as its negative slope conductance and the crossover of the I-V relation upon increases in external K + have long been identified 15 , and their physiological significance has been extensively studied 16, 17 (see Trautwein 18 ). The strong rectification of I K1 is the result of voltage-dependent block by intracellular Mg 2+ 19 and polyamines 20 , primarily spermine and spermidine 21 .…”

Section: Introductionmentioning

confidence: 99%

Regional variation of the inwardly rectifying potassium current in the canine heart and the contributions to differences in action potential repolarization

Cordeiro

Zeina

Goodrow

et al. 2015

Journal of Molecular and Cellular Cardiology

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Background The inward rectifier potassium current, IK1, contributes to the terminal phase of repolarization of the action potential (AP), as well as the value and stability of the resting membrane potential. Regional variation in IK1 has been noted in the canine heart, but the biophysical properties have not been directly compared. We examined the properties and functional contribution of IK1 in isolated myocytes from ventricular, atrial and Purkinje tissue. Methods and Results APs were recorded from canine left ventricular midmyocardium, left atrial and Purkinje tissue. The terminal rate of repolarization of the AP in ventricle, but not in Purkinje, depended on changes in external K+ ([K+]o). Isolated ventricular myocytes had the greatest density of IK1 while atrial myocytes had the lowest. Furthermore, the outward component of IK1 in ventricular cells exhibited a prominent outward component and steep negative slope conductance, which was also enhanced in 10 mM [K+]o. In contrast, both Purkinje and atrial cells exhibited little outward IK1, even in the presence of 10 mM [K+]o, and both cell types showed more persistent current at positive potentials. Expression of Kir2.1 in the ventricle was 76.9-fold higher than that of atria and 5.8-fold higher than that of Purkinje, whereas the expression of Kir2.2 and Kir2.3 subunits was more evenly distributed in Purkinje and atria. Finally, AP clamp data showed distinct contributions of IK1 for each cell type. Conclusions IK1 and Kir2 subunit expression vary dramatically in regions of the canine heart and these regional differences in Kir2 expression likely underlie regional distinctions in IK1 characteristics, contributing to variations in repolarization in response to in [K+]o changes.

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Background K+ current in isolated canine cardiac Purkinje myocytes

Cited by 36 publications

References 32 publications

The Purkinje cell; 2008 style

The Purkinje cell; 2008 style

Electrophysiology of single heart cells from the rabbit tricuspid valve.

Regional variation of the inwardly rectifying potassium current in the canine heart and the contributions to differences in action potential repolarization

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