Developmental changes of the ultrarapid delayed rectifier K + current in rat ventricular myocytes

1997 ◽  
Vol 433 (4) ◽  
pp. 442-445 ◽  
Author(s):  
W. Guo ◽  
Kaichiro Kamiya ◽  
Weiran Liu ◽  
Junji Toyama
Keyword(s):  
Ventricular Myocytes ◽  
Developmental Changes ◽  
Delayed Rectifier ◽  
Rat Ventricular Myocytes ◽  
K Current

Outward currents in normal and hypertrophied feline ventricular myocytes

1989 ◽  
Vol 256 (5) ◽  
pp. H1450-H1461 ◽  
Author(s):  
R. B. Kleiman ◽  
S. R. Houser
Keyword(s):  
Time Course ◽  
Ventricular Myocytes ◽  
Pressure Overload ◽  
Negative Slope ◽  
Inward Rectification ◽  
Delayed Rectifier ◽  
Outward Currents ◽  
K Current ◽  
Prolongation Of Action Potential ◽  
The Right

The properties of the inward rectifier K current (IK1) and the delayed rectifier K current (IK) were studied in single feline myocytes isolated from the right ventricle of normal cats and cats with experimentally induced right ventricular hypertrophy (RVH). IK1 demonstrated time-dependent decay during hyperpolarizations and showed inward rectification with a prominent negative-slope region between -30 and -10 mV. Both IK1 and IK was carried primarily by K ions. The activation of IK during depolarizations followed a monoexponential time course, whereas the deactivation of IK tail currents was either mono- or biexponential depending on the repolarization potential. IK showed marked rectification at positive potentials. A comparison of these currents in normal and hypertrophy myocytes revealed that in RVH the magnitude of IK1 is increased, whereas the magnitude of IK is decreased. IK showed steeper rectification, had slower activation, and had more rapid deactivation in RVH. These abnormalities of the IK may contribute to the prolongation of action potential duration, which characterizes pressure-overload cardiac hypertrophy.

scholarly journals Effects of aldosterone on transient outward K + current density in rat ventricular myocytes

2001 ◽  
Vol 537 (1) ◽  
pp. 151-160 ◽  
Author(s):  
Jean‐Pierre Bénitah ◽  
Emeline Perrier ◽  
Ana María Gómez ◽  
Guy Vassort
Keyword(s):  
Current Density ◽  
Ventricular Myocytes ◽  
Rat Ventricular Myocytes ◽  
K Current

Identification and characteristics of delayed rectifier K+ current in fetal mouse ventricular myocytes

1996 ◽  
Vol 270 (6) ◽  
pp. H2088-H2093 ◽  
Author(s):  
L. Wang ◽  
H. J. Duff
Keyword(s):  
Action Potential ◽  
Cardiac Myocytes ◽  
Ventricular Myocytes ◽  
Dominant Role ◽  
Ventricular Myocardium ◽  
Negative Slope ◽  
Delayed Rectifier ◽  
Mouse Heart ◽  
Fetal Mouse ◽  
K Current

Although the genetics of mammalian cardiac K+ channels have been most intensively investigated in mice, there are limited data available from the electrophysiological studies of the K+ currents in native mouse cardiac myocytes, especially in fetal mouse heart. The present study utilized whole cell patch-clamp techniques to assess the delayed rectifier K+ current (IK) in fetal (18th day of gestation) mouse ventricular myocytes. IK in fetal mouse ventricular myocytes activated rapidly, displayed a negative slope conductance of the current-voltage relationships at test potentials > 0 mV, satisfied the envelope of IK-tail test for a single component, and was very sensitive to dofetilide. These characteristics confirm that this current is the rapidly activating component of IK known as IK,r. In addition, dofetilide dramatically prolonged action potential duration in single ventricular myocytes as well as in ventricular myocardium, suggesting that IK,r plays a dominant role in action potential repolarization in fetal mouse heart. From these data we can conclude that fetal mouse cardiac myocytes express IK,r, which functions as a dominant repolarizing K+ current.

Openings of cardiac KATP channel by oxygen free radicals produced by xanthine oxidase reaction

1996 ◽  
Vol 271 (2) ◽  
pp. H478-H489 ◽  
Author(s):  
K. Tokube ◽  
T. Kiyosue ◽  
M. Arita
Keyword(s):  
Free Radicals ◽  
Binding Sites ◽  
Oxygen Free Radicals ◽  
Ventricular Myocytes ◽  
Outward Current ◽  
Katp Channels ◽  
Free Radical Scavengers ◽  
Delayed Rectifier ◽  
Open Probability ◽  
K Current

We examined the effects of oxygen free radicals (OFRs) on action potentials and membrane currents of guinea pig ventricular myocytes. OFRs produced biphasic changes in the action potential duration, initial lengthening (30 s after exposure to OFRs) and subsequent shortening (within 5 min). In voltage-clamp experiments, OFRs suppressed the L-type calcium current, the delayed rectifier K+ current, and the inward rectifier K+ current. In addition, OFRs increased the time-independent outward current (I(term)) at potentials greater than -30 mV. The increases in I(term) reflected activation of the ATP-sensitive K+ (KATP) channels, as glibenclamide (1 microM) blocked this current. In inside-out patches, OFRs significantly increased the open probability of the channel at a relatively narrow range of ATP concentrations (0.2–2 mM), and this effect was enhanced in the presence of ADP (0.1 mM) and abolished in the presence of either free radical scavengers or gliben-clamide. These findings are compatible with the notion that OFRs activate KATP channels by modulating ATP binding sites of the KATP channels, without affecting ADP binding or glibenclamide binding sites.

Differential modulation by adenylate cyclase of Ca2+ and delayed K+ current in ventricular myocytes

1994 ◽  
Vol 266 (4) ◽  
pp. H1551-H1557 ◽  
Author(s):  
K. Harada ◽  
T. Iijima
Keyword(s):  
Adenylate Cyclase ◽  
Ventricular Myocytes ◽  
Cell Voltage ◽  
Threshold Concentration ◽  
Water Soluble ◽  
Delayed Rectifier ◽  
Differential Modulation ◽  
Beta Adrenoceptor ◽  
Ventricular Cells ◽  
K Current

This study was designed to investigate the differential modulation of the L-type Ca2+ (ICa) and the delayed rectifier K+ (IK) currents by direct activation of adenylate cyclase in guinea pig ventricular preparations. Action potentials were measured with conventional microelectrodes in excised papillary muscles. Isoproterenol significantly shortened the action potential duration at 90% repolarization (APD90) at 0.1 nM but significantly prolonged it at a higher concentration (10 nM). A water-soluble forskolin derivative, 6-(3-dimethylaminopropionyl) forskolin (NKH-477), slightly but significantly shortened APD at 12 nM but not at a higher concentration (120 nM). Effects of isoproterenol and NKH-477 on ICa and IK were also investigated by use of the whole cell voltage-clamp technique in single ventricular cells. Isoproterenol increased not only IK but also ICa at the same threshold concentration (0.3 nM). In contrast, the threshold concentration of NKH-477 for increasing IK (approximately 1 nM) was clearly lower than that for increasing ICa (10 nM). These results indicate that ICa and IK channels could be differentially regulated during beta-adrenoceptor stimulation.

Influence of Extracellular K+Concentrations on Quinidine-induced K+Current Inhibition in Rat Ventricular Myocytes

2000 ◽  
Vol 52 (1) ◽  
pp. 99-105 ◽  
Author(s):  
MICHIKO HIROTA ◽  
HISAKAZU OHTANI ◽  
ERIKA HANADA ◽  
HITOSHI SATO ◽  
HAJIME KOTAKI ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Rat Ventricular Myocytes ◽  
K Current
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