Automatic activity of pacemaker cells of the atrioventricular valves of the rabbit heart

Makarychev, V. A.; Kosharskaia, I L; Ul'ianinskiĭ, L S

doi:10.1007/bf00797116

Cited by 7 publications

(7 citation statements)

References 7 publications

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“…The results of our study show that the myocytes in the tricuspid valve can easily be isolated, and that they have properties similar to those described in previous whole-tissue electrophysiological studies (Wit et al 1973;Makarychev et al 1976;Rozanski & Jalife, 1986). A few limitations of this study are, however, noteworthy: experiments were essentially carried out at room temperature (20-23 0C) which is expected to affect properties of the ionic currents studied.…”

Section: Discussionmentioning

confidence: 76%

“…Anumonwo, M. Delmar & J. Jalife, unpublished). Electrophysiological studies on isolated AV valve tissue have shown that the fibres therein are capable of rhythmic activity (Wit, Fenoglio, Wagner & Bassett, 1973;Makarychev, Kosharskaya & Ul'Yaniskii, 1976;Wit, Fenoglio, Hordoff & Reemtsma, 1979;Rozanski & Jalife, 1986). In addition it has been shown that when the simian mitral valve is externally driven in the presence of catecholamines, delayed afterdepolarizations are developed resulting in sustained triggered activity (Wit & Cranefield, 1976).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Electrophysiology of single heart cells from the rabbit tricuspid valve.

Anumonwo

Delmar

Jalife

1990

The Journal of Physiology

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“…It has been reported that in several mammalian species, including the human, myocytes in the atrioventricular annuli have automatic or triggered activities [5][6][7][8][9][10][11][12]. The automaticity in rabbit tricuspid valve myocytes is sensitive to Cs + block of I f (Cs + results in a slowing of the beating rate [6,7]) and, furthermore, I f has been recorded from the tricuspid valve myocytes [7].…”

Section: Av Ring Bundlesmentioning

confidence: 99%

“…In the atria, there are rings of nodal-like cells around the atrioventricular valves (AV ring bundles) [5][6][7][8][9][10][11][12]. Fig.…”

Section: Av Ring Bundles and Avnmentioning

confidence: 99%

“…In the heart, there are multiple supraventricular tissues capable of showing pacemaker activity including the sinoatrial node (SAN), atrioventricular node (AVN), superior vena cava [1][2][3][4], AV ring bundles [5][6][7][8][9][10][11][12] and pulmonary veins [13]. These tissues constitute the normal pacemaker (SAN), back-up pacemakers (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Extended atrial conduction system characterised by the expression of the HCN4 channel and connexin45

Yamamoto

Dobrzynski

Tellez

et al. 2006

Cardiovascular Research

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Location and functional characterization of the right atrioventricular pacemaker ring in the adult avian heart

Prosheva

Kaseva

2015

Journal of Morphology

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Previous histological studies showed that in addition to a sinus node, an atrioventricular (AV) node, an AV bundle, left and right bundle branches, birds also possess a right AV-Purkinje ring that is located in the atrial sheet of the right muscular AV-valve along all its base length. The functionality of the AV-Purkinje ring is unknown. In this work, we studied the topology of pacemaker myocytes in the atrial side of the isolated chicken spontaneously contracting right muscular AV-valve using the method of microelectrode mapping of action potentials. We show that AV-cells having the ability to show pacemaking reside in the right muscular AV-valve. Pacemaker action potentials were exclusively recorded close to the base of the valve along its whole length from dorsal to the ventral attachment to the interventricular septum. These action potentials have much slower rate of depolarization, lower amplitude, and higher diastolic depolarization than action potentials of Purkinje (conducting) cells. We conclude the right AV-valve has a ring bundle of pacemaker cells (but not Purkinje cells) in the adult chicken heart.

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Automatic activity of pacemaker cells of the atrioventricular valves of the rabbit heart

Cited by 7 publications

References 7 publications

Electrophysiology of single heart cells from the rabbit tricuspid valve.

Electrophysiology of single heart cells from the rabbit tricuspid valve.

Extended atrial conduction system characterised by the expression of the HCN4 channel and connexin45

Location and functional characterization of the right atrioventricular pacemaker ring in the adult avian heart

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