Calcium- and voltage-activated plateau currents of cardiac Purkinje fibers.

Kenyon, James L.; Sutko, J L

doi:10.1085/jgp.89.6.921

Cited by 59 publications

(24 citation statements)

References 65 publications

(145 reference statements)

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“…Calcium-activated outward potassium current, activated by large depolarizing pulses and largely sensitive to calcium influx, was also observed in clam cardiomyocytes as in vertebrates (Siegelbaum and Tsien 1980;Kenyon and Sutko 1987;Giles and Imaizumi 1988) or invertebrates (Pennec et al 2004;Ö dblom et al 2000). This current has a role in the regulation of cell contractility and intracellular calcium regulation.…”

Section: Discussionmentioning

confidence: 89%

Establishment of functional primary cultures of heart cells from the clam Ruditapes decussatus

Hanana¹,

Talarmin²,

Pennec³

et al. 2011

Cytotechnology

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Heart cells from the clam Ruditapes decussatus were routinely cultured with a high level of reproducibility in sea water based medium. Three cell types attached to the plastic after 2 days and could be maintained in vitro for at least 1 month: epithelial-like cells, round cells and fibroblastic cells. Fibroblastic cells were identified as functional cardiomyocytes due to their spontaneous beating, their ultrastructural characteristics and their reactivity with antibodies against sarcomeric a-actinin, sarcomeric tropomyosin, myosin and troponin T-C. Patch clamp measurements allowed the identification of ionic currents characteristic of cardiomyocytes: a delayed potassium current (I K slow ) strongly suppressed (95%) by tetraethylammonium (1 mM), a fast inactivating potassium current (I K fast ) inhibited (50%) by 4 amino-pyridine at 1 mM and, at a lower level (34%) by TEA, a calcium dependent potassium current (I KCa ) activated by strong depolarization. Three inward voltage activated currents were also characterized in some cardiomyocytes: L-type calcium current (I Ca ) inhibited by verapamil at 5 9 10 -4 M, T-type Ca 2? current, rapidly activated and inactivated, and sodium current (I Na ) observed in only a few cells after strong hyperpolarization. These two currents did not seem to be physiologically essential in the initiation of the beatings of cardiomyocytes. Potassium currents were partially inhibited by tributyltin (TBT) (1 lM) but not by okadaic acid (two marine pollutants). DNA synthesis was also demonstrated in few cultured cells using BrdU (bromo-2 0 -deoxyuridine). Observed effects of okadaic acid and TBT demonstrated that cultured heart cells from clam Ruditapes decussatus can be used as an experimental model in marine toxicology.

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Section: Discussionmentioning

confidence: 89%

Establishment of functional primary cultures of heart cells from the clam Ruditapes decussatus

Hanana¹,

Talarmin²,

Pennec³

et al. 2011

Cytotechnology

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“…For example, it has been shown in canine ventricular tissue (Greenspan, Edmands & Fisch, 1967) and feline ventricular tissue (Boyett, 1978) that the action potential duration decreases as the strength of contraction increases. That an effect of this type could be related to the change in the Ca2+ transient was suggested by Marban & Wier (1985) and Kenyon & Sutko (1987), who found that the action potential duration was increased in Purkinje fibres when the Ca2+ transient was decreased or eliminated with ryanodine. In addition, Lab, Allen & Orchard (1984) have shown that the duration of the canine ventricular action potential decreased when the duration of the Ca2+ transient was increased by allowing the muscle preparation to shorten.…”

Section: Introductionmentioning

confidence: 84%

“…These typically have a plateau at more positive potentials, near 0 mV (e.g. Josephson et al 1984 a;Mitchell et al 1987 a;Tseng, Robinson & Hoffman, 1987) and have been shown to decrease, rather than increase, in duration as the CaF+ transient is decreased (Boyett, 1978;Marban & Wier, 1985;Kenyon & Sutko, 1987). To the extent that Na'-Ca2+ exchange current is involved in the process, it is less likely to have a major role in a plateau at more positive potentials because for a given CaO+ the magnitude of inward Na+-Ca2+ exchange current is substantially smaller at more positive potentials as the reversal potential is approached (Mullins, 1979;Kimura et al 1987).…”

Section: Cytosolic Ca2+ and The Action Potentialmentioning

confidence: 99%

The cytosolic calcium transient modulates the action potential of rat ventricular myocytes.

duBell

Boyett

Spurgeon

et al. 1991

The Journal of Physiology

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SUMMARY1. The modulation of the action potential by the cytosolic Ca2+ (Ca0') transient was studied in single isolated rat ventricular myocytes loaded with the acetoxymethyl ester form of the Ca2+-sensitive fluorescent dye Indo-1. Stimulation following rest and exposure to ryanodine were used to change the amount of Ca2+ released from the sarcoplasmic reticulum and thus the size of the CaF' transient. The CaF+ transient was measured as the change, upon stimulation, in the ratio of Indo-1 fluorescence at 410 nm to that at 490 nm (410/490) and action potentials or membrane currents were recorded using patch-type microelectrodes.2. When stimulation was initiated following rest, the magnitude of the CaF' transient decreased in a beat-dependent manner until a steady state was reached. The negative staircase in the CaF+ transient was accompanied by a similar beatdependent decrease in the duration of the action potential, manifested primarily as a gradual loss of the action potential plateau (~-45 mV). A slow terminal phase of repolarization of a few millivolts in amplitude was found to parallel the terminal decay of the CaF+ transient.3. The terminal portion of phase-plane loops of membrane potential (Vm) vs. Indo-1 ratio from all of the beats of a stimulus train followed a common linear trajectory even though the individual beats differed markedly in the duration and amplitude of the action potential and Ca0+ transient.4. When the stimulation dependence of the CaO' transient was titrated away with submaximal exposure to ryanodine, the stimulation-dependent changes in the action potential plateau and terminal phase of repolarization were also eliminated. The same effect was noted in cells which, fortuitously, did not show a staircase in the CaF+ transient following a period of rest.5. When action potentials were triggered immediately following spontaneous release of Ca2+ from the sarcoplasmic reticulum, which results in a small depolarization at the resting potential, phase-plane loops (Vm vs. Indo-1 ratio) of the spontaneous events followed the same linear trajectory as the terminal phase of repolarization in the loops of the stimulated beats. IMS 8396 }4T. H. Dt-BELL AND OTHERS 6. Following repolarization from brief voltage clamp pulses (to minimize timeand voltage-dependent currents associated with depolarization), an inward currynt was observed that rose and fell in phase with the Ca4+ transient. This current was present at -70 mV. near the resting potential. and at -40 mV, a potential relevant to the plateau of the action potential. During trains of 50 ms voltage clamp pulses (-70 to 0 mV) following rest, this inward current showed a negative staircase paralleling that of the Ca2+ transient. Phase-plane plots (inward current vs. Indo-1 ratio) from each beat were linear and plots from successive beats in a voltage clamp train superimposed on this line. This relationship is analogous to that seen in phaseplane loops of action potential trains during the terminal phase of repolarization.7. Application of LiCl to ...

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“…Another current of importance for the action potential plateau is the transient outward current (I,,,), which has been identified in several types of heart cells: in calf, 12 sheep, 13 " 15 and dog Purkinje fibers 16 ; in rat" and rabbit ventricular cells, 18 in rabbit atrial cells," and in rabbit atrioventricular cells. 20 In some cardiac tissues I,, may be regulated by intracellular calcium and therefore associated with I ri .…”

Section: Adrenergic Modulation Of the Transient Outward Current In Ismentioning

confidence: 99%

Adrenergic modulation of the transient outward current in isolated canine Purkinje cells.

Nakayama

Fozzard

1988

Circulation Research

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Single canine Purkinje cells were voltage clamped under Ca 2+ -free conditions using the patch pipette. Depolarizing pulses from a holding potential of -42 mV induced a time-dependent rapidly activating-slowly inactivating outward current, which was identified as the transient outward current. The current showed two exponential time constants of inactivation (48, 352 msec at + 58 mV and 53, 325 msec at + 78 mV). Norepinephrine in concentrations exceeding 10*' M modified the inactivation kinetics of this current without affecting the activation kinetics. The half-maximum dose for norepinephrine effect was 1.9x10"' M, and the effect was saturated at 10"' M. Norepinephrine reduced the amplitude of the fast time constant component of inactivation, while increasing the amplitude of the slow component, without changing their time constants. Norepinephrine also increased the amplitude of a time-independent current component. The /3-antagonist sotalol blocked the norepinephrine effect on the transient outward current. On the other hand, both activation of adenyl cyclase by forskolin and increase of intracellular cAMP concentration produced the same effect as exposure to norepinephrine. These results suggest a role for neurotransmitter regulation of the transient outward current in cardiac cells, perhaps by channel phosphorylation. (Circulation Research 1988;62:162-172) N orepinephrine is known as an important transmitter of neural control in the heart.' One of the most important actions of norepinephrine is the modulation of ion channels, but its effects on the action potential are complex. It has been clearly shown that norepinephrine affects the slow inward current (IJ and the delayed rectifier potassium current (I K ).3 -610 " However, these two actions are not sufficient to explain norepinephrine's complex effects on the cardiac action potential.Another current of importance for the action potential plateau is the transient outward current (I,,, Recently, we have studied 1^, in isolated canine Purkinje cells. This current is modified by norepinephrine (NE) but not by intracellular Ca 2+ . Our studies suggest that the transient outward current channel can be phosphorylated by a cAMP-dependent process, altering the kinetics of the current. Materials and Methods Preparation of Single Purkinje CellsSingle Purkinje cells were isolated according to procedures previously described. 25 Briefly, canine freerunning Purkinje fibers were obtained from adult dogs anesthetized with sodium pentobarbital (30 mg/kg). The Purkinje fibers were cut into 2-3 mm lengths and placed in bicarbonate Tyrode's solution gassed with 5% CO 2 and 95% O 2 . The cut fibers were then placed for a period of 4 hours in the bottom of a plastic culture dish, which contained Eagles minimal essential medium (Gibco, Grand Island, N. Y.) modified to contain 0.1 mMfreeCa 2+ , 5.6mMMg 2 + , 5 mg/ml collagenase (type 1, Worthington, Freehold, N.J.), and 1 mg/ml albumin (Sigma, St. Louis, Mo.). The pH was adjusted to6.2 by addition of 5.0 mM HEPES-NaOH buffe...

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Calcium- and voltage-activated plateau currents of cardiac Purkinje fibers.

Cited by 59 publications

References 65 publications

Establishment of functional primary cultures of heart cells from the clam Ruditapes decussatus

Establishment of functional primary cultures of heart cells from the clam Ruditapes decussatus

The cytosolic calcium transient modulates the action potential of rat ventricular myocytes.

Adrenergic modulation of the transient outward current in isolated canine Purkinje cells.

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