An identification of the K activated Na pump current in sheep Prkinje fibres

1982 ◽  
Vol 394 (3) ◽  
pp. 256-263 ◽  
Author(s):  
H. G. Glitsch ◽  
H. Pusch ◽  
Th. Schumacher ◽  
F. Verdonck
Keyword(s):  
Pump Current ◽  
Na Pump

Identification of Low and High Affinity Ouabain-Sensitive Na Pump Current in Voltage-Clamped Rat Cardiac Myocytes

1992 ◽  
Vol 671 (1 Ion-Motive AT) ◽  
pp. 440-442 ◽  
Author(s):  
JOSHUA R. BERLIN ◽  
ALEXANDER J. FIELDING ◽  
NOBUHIKO ISHIZUKA
Keyword(s):  
Cardiac Myocytes ◽  
Pump Current ◽  
High Affinity ◽  
Na Pump ◽  
Rat Cardiac Myocytes

Mechanisms underlying delayed afterdepolarizations in hypertrophied left ventricular myocytes of rats

2001 ◽  
Vol 281 (2) ◽  
pp. H903-H914 ◽  
Author(s):  
János Mészáros ◽  
Daniel Khananshvili ◽  
George Hart
Keyword(s):  
Ventricular Myocytes ◽  
Pump Current ◽  
Left Ventricular ◽  
Daily Injection ◽  
Nonselective Cation Channel ◽  
Patch Clamp Technique ◽  
Inward Current ◽  
Na Pump ◽  
Whole Cell Patch Clamp ◽  
Delayed Afterdepolarizations

Cardiac hypertrophy was induced in rats by daily injection of isoproterenol (5 mg/kg ip) for 7 days. Membrane voltage and currents were recorded using the whole cell patch-clamp technique in left ventricular myocytes from control and hypertrophied hearts. Ryanodine-sensitive delayed afterdepolarizations (DADs) and transient inward current ( I ti) appeared in hypertrophied cells more often and were of larger amplitude than in control cells. DADs and I ti are carried principally by Na/Ca exchange with smaller contributions from a nonselective cation channel and from a Cl− channel. The latter is expressed only in hypertrophied myocytes. In hypertrophy, the density of caffeine-induced Na/Ca exchange current ( I Na/Ca) was increased by 26%, sarcoplasmic reticulum (SR) Ca2+ content as assessed from the integral of I Na/Ca was increased by 30%, the density of Na-pump current ( I pump) was reduced by 40%, and the intracellular Na+ content, measured by Na+-selective microelectrodes was increased by 55%. The results indicate that DADs and I ti are generated by spontaneous Ca2+ release from an overloaded SR caused by a downregulated Na pump and an upregulated Na/Ca exchange. These findings may explain the propensity for arrhythmias seen in this model of hypertrophy.

scholarly journals Stimulation of Na+ transport by AVP is independent of PKA phosphorylation of the Na-K-ATPase in collecting duct principal cells

2005 ◽  
Vol 289 (5) ◽  
pp. F1031-F1039 ◽  
Author(s):  
David Mordasini ◽  
Mauro Bustamante ◽  
Martine Rousselot ◽  
Pierre-Yves Martin ◽  
Udo Hasler ◽  
...  
Keyword(s):  
Cell Surface ◽  
Time Course ◽  
Collecting Duct ◽  
Pump Current ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Intact Cells ◽  
Principal Cells ◽  
Na Pump ◽  
Stimulation Of

Arginine-vasopressin (AVP) stimulates Na+ transport and Na-K-ATPase activity via cAMP-dependent PKA activation in the renal cortical collecting duct (CCD). We investigated the role of the Na-K-ATPase in the AVP-induced stimulation of transepithelial Na+ transport using the mpkCCDc14 cell model of mammalian collecting duct principal cells. AVP (10−9 M) stimulated both the amiloride-sensitive transepithelial Na+ transport measured in intact cells and the maximal Na pump current measured by the ouabain-sensitive short-circuit current in apically permeabilized cells. These effects were associated with increased Na-K-ATPase cell surface expression, measured by Western blotting after streptavidin precipitation of biotinylated cell surface proteins. The effects of AVP on Na pump current and Na-K-ATPase cell surface expression were dependent on PKA activity but independent of increased apical Na+ entry. Time course experiments revealed that in response to AVP, the cell surface expression of both endogenous Na-K-ATPase and hybrid Na pumps containing a c- myc-tagged wild-type human α1-subunit increased transiently. Na-K-ATPase cell surface expression was maximal after 30 min and then declined toward baseline after 60 min. Immunoprecipitation experiments showed that PKA activation did not alter total phosphorylation levels of the endogenous Na-K-ATPase α-subunit. In addition, mutation of the PKA phosphorylation site (S943A or S943D) did not alter the time course of increased cell surface expression of c- myc-tagged Na-K-ATPase in response to AVP or to dibutyryl-cAMP. Therefore, stimulation of Na-K-ATPase cell surface expression by AVP is dependent on PKA but does not rely on α1-subunit phosphorylation on serine 943 in the collecting duct principal cells.

Metabolic support of Na+ pump in apically permeabilized A6 kidney cell epithelia: role of creatine kinase

1997 ◽  
Vol 272 (2) ◽  
pp. C697-C706 ◽  
Author(s):  
M. L. Guerrero ◽  
J. Beron ◽  
B. Spindler ◽  
P. Groscurth ◽  
T. Wallimann ◽  
...  
Keyword(s):  
Creatine Kinase ◽  
Oxidative Phosphorylation ◽  
Atp Synthesis ◽  
Pump Current ◽  
Na Pump ◽  
A6 Epithelia ◽  
Confocal Fluorescence ◽  
Pump Activity ◽  
Atp Supply

The contribution of ATP-generating systems to Na+ pump (Na+-K+-ATPase) function was studied in Xenopus laevis A6 kidney epithelia apically permeabilized with digitonin. The ouabain-inhibitable Na+ pump current (I(P)) was measured in the presence of otherwise impermeant inhibitors and/or substrates at Na+ and K+ concentrations that allowed near-maximal pump function. Confocal fluorescence microscopy after apical addition of sulfosuccinimidobiotin (molecular weight of 443) showed that all cells were permeabilized. Less than 15% of the endogenous lactate dehydrogenase and creatine kinase (CK) were released into the apical medium. The I(P) was approximately 5 microA/cm2 in the presence of D-glucose. Blocking glycolysis with 2-deoxy-D-glucose or oxidative phosphorylation with antimycin A decreased it by > or = 50%. Exogenously added ATP prevented these decreases fully or partially, respectively. Two CK isoforms were detected, one likely being mitochondrial and the other corresponding to mammalian B isoform of CK. Phosphocreatine partially restored Na+ pump activity during inhibition of either ATP synthesis pathway. In conclusion, the ATP used by Na+ pumps of apically digitonin-permeabilized A6 epithelia is generated to a similar extent by glycolysis and oxidative phosphorylation. The CK system can partially support the ATP supply to the Na+ pumps.

Influence of prior Na+ pump activity on pump and Na+/Ca2+exchange currents in mouse ventricular myocytes

1998 ◽  
Vol 275 (5) ◽  
pp. H1808-H1817 ◽  
Author(s):  
Zhi Su ◽  
Anruo Zou ◽  
Akihiko Nonaka ◽  
Iram Zubair ◽  
Michael C. Sanguinetti ◽  
...  
Keyword(s):  
Steady State ◽  
Concentration Gradient ◽  
Ventricular Myocytes ◽  
State Level ◽  
Pump Current ◽  
Steady State Level ◽  
Peak Current ◽  
Na Pump ◽  
Patch Pipette ◽  
Pump Activity

We examined the dependence of peak Na+ pump and Na+/Ca2+exchanger currents on prior Na+pump inhibition induced by exposure to zero extracellular K+ in voltage-clamped adult murine ventricular myocytes. Abrupt activation of the Na+ pump by reexposure of myocytes to extracellular K+ with a rapid solution switcher resulted in the development of a transient peak current at ∼500 ms, followed by a decline over 1–2 min to a steady-state level. The magnitudes of both the peak Na+ pump current ( I p) and the peak outward Na+/Ca2+exchange current, activated by rapidly reducing extracellular Na+ to zero with the solution switcher, were dependent on previous Na+ pump activity. [Na+] gradients (Na+-binding benzofuran isophthalate fluorescence) between the patch pipette and the bulk cytosol were relatively small and could not account for the large differences between peak and steady-state I p and reverse Na+/Ca2+exchanger currents. Our results are consistent with the presence of a subsarcolemmal Na+ concentration gradient, which is similar for the Na+ pump and the Na+/Ca2+exchanger. These findings also support the hypothesis that the Na+ pump and the Na+/Ca2+exchanger are colocalized in the sarcolemma.

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