scholarly journals Na+ pump current-voltage relationships of rabbit cardiac Purkinje cells in Na(+)-free solution.

1993 ◽  
Vol 465 (1) ◽  
pp. 699-714 ◽  
Author(s):  
F V Bielen ◽  
H G Glitsch ◽  
F Verdonck
Keyword(s):  
Purkinje Cells ◽  
Pump Current ◽  
Free Solution ◽  
Na Pump ◽  
Current Voltage ◽  
Cardiac Purkinje Cells

scholarly journals Na/K pump current in aggregates of cultured chick cardiac myocytes.

1990 ◽  
Vol 95 (1) ◽  
pp. 61-76 ◽  
Author(s):  
J R Stimers ◽  
N Shigeto ◽  
M Lieberman
Keyword(s):  
Steady State ◽  
Cardiac Myocytes ◽  
Pump Current ◽  
Cardiac Cells ◽  
Hill Coefficient ◽  
Published Data ◽  
Free Solution ◽  
Embryonic Chick ◽  
Current Voltage ◽  
Current Voltage Relationship

Spontaneously beating aggregates of cultured embryonic chick cardiac myocytes, maintained at 37 degrees C, were voltage clamped using a single microelectrode switching clamp to measure the current generated by the Na/K pump (Ip). In resting, steady-state preparations an ouabain-sensitive current of 0.46 +/- 0.03 microA/cm2 (n = 22) was identified. This current was not affected by 1 mM Ba, which was used to reduce inward rectifier current (IK1) and linearize the current-voltage relationship. When K-free solution was used to block Ip, subsequent addition of Ko reactivated the Na/K pump, generating an outward reactivation current that was also ouabain sensitive. The reactivation current magnitude was a saturating function of Ko with a Hill coefficient of 1.7 and K0.5 of 1.9 mM in the presence of 144 mM Nao. The reactivation current was increased in magnitude when Nai was increased by lengthening the period of time that the preparation was exposed to K-free solution prior to reactivation. When Nai was raised by 3 microM monensin, steady-state Ip was increased more than threefold above the resting value to 1.74 +/- 0.09 microA/cm2 (n = 11). From these measurements and other published data we calculate that in a resting myocyte: (a) the steady-state Ip should hyperpolarize the membrane by 6.5 mV, (b) the turnover rate of the Na/K pump is 29 s-1, and (c) the Na influx is 14.3 pmol/cm2.s. We conclude that in cultured embryonic chick cardiac myocytes, the Na/K pump generates a measurable current which, under certain conditions, can be isolated from other membrane currents and has properties similar to those reported for adult cardiac cells.

Delayed K+ current and external K+ in single cardiac Purkinje cells

1989 ◽  
Vol 257 (6) ◽  
pp. C1086-C1092 ◽  
Author(s):  
F. Scamps ◽  
E. Carmeliet
Keyword(s):  
Voltage Clamp ◽  
Purkinje Cells ◽  
Cell Voltage ◽  
Inhibitory Effect ◽  
Free Solution ◽  
Cardiac Purkinje Cells ◽  
K Current ◽  
Kinetics Of ◽  
Direct Change ◽  
External K

The effect of external K+ on the delayed K+ current was investigated in rabbit single Purkinje cells. Whole cell voltage clamp and intracellular dialysis were used. At K+ concentrations less than 1 mM the kinetics of the delayed K+ current were not changed, but the conductance was markedly reduced. This effect was due to a direct change at an extracellular site and not due to secondary changes in intracellular Na+ or Ca2+ concentrations. A rise in intracellular Na+ or Ca2+ rather increased the delayed K+ current. The decrease in the delayed K+ current in low external K+ was absent when the experiments were done in Na+-free solution. It is concluded that external Na+ exerts an inhibitory effect on the conductance of the delayed K+ current.

scholarly journals Cardiac Na+ pump current-voltage relationships at various transmembrane gradients of the pumped cations

1996 ◽  
Vol 1278 (2) ◽  
pp. 137-146 ◽  
Author(s):  
Helfried Günther Glitsch ◽  
Wolfgang Schwarz ◽  
André Tappe
Keyword(s):  
Pump Current ◽  
Na Pump ◽  
Current Voltage

Simulation of Na/K Pump Current-Voltage Relationship

1992 ◽  
Vol 671 (1 Ion-Motive AT) ◽  
pp. 449-451 ◽  
Author(s):  
X.-Y. LIU ◽  
T. A. KINARD ◽  
J. R. STIMERS
Keyword(s):  
Pump Current ◽  
Current Voltage ◽  
Current Voltage Relationship ◽  
Voltage Relationship

Volumetric properties of intracellular compartments in canine cardiac Purkinje cells

1980 ◽  
Vol 238 (4) ◽  
pp. H561-H568
Author(s):  
S. R. Houser ◽  
A. R. Freeman
Keyword(s):  
Purkinje Cells ◽  
Regression Line ◽  
Resting Potential ◽  
Volumetric Properties ◽  
Bathing Medium ◽  
Cellular Volume ◽  
Cardiac Purkinje Fibers ◽  
Cardiac Purkinje Cells ◽  
Intracellular Compartments ◽  
The Relationship

Volumetric properties of canine cardiac Purkinje fibers were examined. Purkinje cells were superfused with anisosmolar solutions, and changes in extracellular space and relative cell volume were determined. The relationship between cellular volume and the osmolarity of the bathing medium was shown to be linear except in solutions of very low osmolarity. A linear regression line crossed the volume axis at 38%, suggesting an osmometric dead space of 38% and correspondingly an osmometric compartment comprising about 62% of the cell interior. To determine the volumetric properties of the "electrophysiological compartment," Purkinje cells were impaled with voltage-sensitive microelectrodes, and cellular resting potentials were recorded. When log K was plotted against resting potential (Em) in preparations bathed in normal and hyperosmotic solutions, it was shown that Em was increased in hyperosmotic solutions (13.5 and 21 mV in 600 and 850 mosM solutions, respectively). Calculations using the Nernst equation showed that the compartment containing the intracellular K involved in membrane electrical events behaves as a near-perfect osmometer in hyperosmotic solutions. Changes in the osmometric compartment were well correlated with K changes in the electrophysiological compartment, thus suggesting that the K is homogeneously distributed intracellularly.

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