scholarly journals The relationship between sodium pump activity and twitch tension in cardiac Purkinje fibres

1980 ◽  
Vol 303 (1) ◽  
pp. 475-494 ◽  
Author(s):  
D. A. Eisner ◽  
W. J. Lederer
Keyword(s):  
Sodium Pump ◽  
Purkinje Fibres ◽  
Pump Activity ◽  
The Relationship ◽  
Cardiac Purkinje Fibres

The effects of sodium pump activity on the slow inward current in sheep cardiac Purkinje fibres

1982 ◽  
Vol 214 (1195) ◽  
pp. 249-262 ◽  
Keyword(s):  
Ion Concentration ◽  
Slow Inward Current ◽  
Purkinje Fibres ◽  
Inward Current ◽  
Na Pump ◽  
Pump Activity ◽  
External Site ◽  
K Concentration ◽  
Low K ◽  
Cardiac Purkinje Fibres

The effects of Na pump activity on the slow inward current, I si , magnitude and twitch tension were investigated in sheep cardiac Purkinje fibres. A two-microelectrode voltage-clamp method was used, tension being measured simultaneously. Na pump activity was lowered either by reducing the extracellular K concentration, [K] o , or by applying the cardiotonic steroid strophanthidin. Reduction of [K] o from 4 to 0 mM leads to time-dependent increases in I si magnitude and twitch tension. The increases of I si and tension could be reversed by adding Tl, Rb, Cs or NH 4 ions to the K-free superfusate. The actions of these ions are attributed to the known ability of these cations to activate the external site of the Na pump. This conclusion is supported by the observation that such activator cations do not reverse the increases in I si and tension produced by strophanthidin. We conclude that the effects of low [K] o on I si are mediated by Na pump inhibition. Similarly the Na pump inhibition produced by strophanthidin increases I si and tension, although, in this case, other mechanisms may also contribute. Measurements of the activity of the electrogenic Na pump show that elevated intracellular Na ion concentration secondary to Na pump inhibition and not the instantaneous Na pump turnover rate mediates the increase in I si magnitude.

Interaction of alcohol and kola nut on brain sodium pump activity in Wistar rats

2009 ◽  
Vol 91 (2) ◽  
pp. 357-362
Author(s):  
G.O. Obochi ◽  
A.E. Abara ◽  
S.P. Malu ◽  
M.U. Eteng ◽  
I.B. Umoh
Keyword(s):  
Wistar Rats ◽  
Sodium Pump ◽  
Pump Activity

Chlormadinone acetate, a progesterone derivative that binds to the digitalis receptor, inhibits the sodium pump in the isolated rat diaphragm

1985 ◽  
Vol 63 (1) ◽  
pp. 44-47 ◽  
Author(s):  
Ivan Bihler ◽  
Frank S. LaBella ◽  
P. C. Sawh
Keyword(s):  
Sodium Pump ◽  
Sugar Transport ◽  
Diaphragm Muscle ◽  
Rat Diaphragm ◽  
Bathing Medium ◽  
Chlormadinone Acetate ◽  
Muscle Tissues ◽  
Pump Activity ◽  
Intact Muscle ◽  
Resting Muscle

Rb+ uptake, intracellular Na+ and K+ levels, and the tissue–medium distribution of the nonmetabolized glucose analog, 3-O-methyl-D-glucose (3-MG) were measured in rat diaphragms incubated with chiormadinone acetate, 6-chloro-4,6-pregnadien-17-ol-3,20-dione 17-acetate (CMA), in the presence and absence of ouabain. CMA in concentrations of 5 × 10−7 M or higher significantly depressed 86Rb uptake, and promoted an increase in internal Na+ and a decrease in internal K+, indicating inhibition of the sodium pump. Sugar transport in resting muscle parallels the changes in internal Na+ levels and is an additional indicator of sodium pump activity. Equilibration of 3-MG between tissue and medium was accelerated by CMA, in parallel to the rise in internal Na+ level. Effects of CMA on Na+ levels and sugar transport, but not on Rb+ uptake, were additive to those of various concentrations of ouabain, suggesting interaction with sites not affected by ouabain. These results on diaphragm muscle confirm our previous studies on isolated cardiac muscle preparations showing that CMA, added to the aqueous bathing medium, inhibits the sodium pump in intact muscle tissues.

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