[10] Preparation and use of micro- and macroelectrodes for measurement of transmembrane potentials and ion activities

1989 ◽  
pp. 136-155 ◽  
Author(s):  
Daniel Ammann ◽  
Pico Caroni
Keyword(s):  
Transmembrane Potentials ◽  
Ion Activities

Intracellular K+ and Na+ activities under hypoxia, acidosis, and no glucose in dog hearts

1985 ◽  
Vol 249 (6) ◽  
pp. H1078-H1085 ◽  
Author(s):  
H. Nakaya ◽  
S. Kimura ◽  
M. Kanno
Keyword(s):  
Action Potential ◽  
Respiratory Acidosis ◽  
Resting Membrane Potential ◽  
Canine Heart ◽  
Free Condition ◽  
Transmembrane Potentials ◽  
Amplitude Maximum ◽  
Ionic Mechanisms ◽  
Ion Activities ◽  
Microelectrode Techniques

To gain a better understanding of the ionic mechanisms responsible for the electrophysiological disturbances occurring during myocardial ischemia, transmembrane potentials and intracellular potassium (aiK) and sodium (aiNa) ion activities were measured under individual and combined conditions of hypoxia (Po2 less than 50 mmHg), respiratory acidosis (pH 6.6), and no glucose in isolated epicardial ventricular muscle preparations of the canine heart using conventional and ion-selective microelectrode techniques. After 30 min superfusion with hypoxic, acidic, and glucose-free solution under 2-Hz stimulation, resting membrane potential (RMP) was significantly reduced from -85.5 +/- 0.6 to -69.5 +/- 1.0 mV, accompanied by decreases in action potential amplitude, maximum upstroke velocity of phase O, and action potential duration. aiK was significantly decreased from 101.0 +/- 5.6 to 79.5 +/- 5.8 mM, whereas aiNa was not significantly altered by the combined condition. RMP and aiK were moderately decreased by hypoxia alone, slightly decreased by acidosis, and hardly affected by the glucose-free condition. The extent of depolarization was well correlated with the decrease in aiK. These results suggest that Na+-K+ pump inhibition may not be a major cause of K+ efflux from myocardial cells under the hypoxic, acidic, and glucose-free condition and that hypoxia is the most important factor affecting aiK and RMP among these conditions.

Shunt resistance and ion permeabilities in normal and cystic fibrosis airway epithelia

1989 ◽  
Vol 256 (5) ◽  
pp. C1054-C1063 ◽  
Author(s):  
N. J. Willumsen ◽  
R. C. Boucher
Keyword(s):  
Cystic Fibrosis ◽  
Steady State ◽  
Apical Membrane ◽  
Short Circuit ◽  
Strongly Correlated ◽  
Shunt Resistance ◽  
Human Nasal Epithelium ◽  
Cystic Fibrosis Airway ◽  
Intracellular Ion Activities ◽  
Ion Activities

A method for determination of shunt resistance (Rs) and absolute conductive ion permeabilities of the apical membrane in epithelia from steady-state data is described. The method assumes that the currents are satisfactorily described by the Goldman-Hodgkin-Katz regime. Its application requires measurements of standard transepithelial electrophysiological parameters and of one or more intracellular ion activities. It is applicable under both open- and short-circuit conditions. The method was tested in an electrophysiological analysis of cultured normal and cystic fibrosis (CF) human nasal epithelium. In 15 normal and 10 CF preparations with mean transepithelial resistances of 338 and 427 omega.cm2, Rs was 412 and 623 omega.cm2, respectively. The Rs values determined with the present method were strongly correlated (r = 0.94) with those obtained with another method available in the electrophysiological literature but were as a mean 20% lower. Amiloride increased Rs by 25% in CF and by 8% in normal preparations. In normal preparations, the apical Cl permeability (PCla) was 3.6 x 10(-6) cm/s, and the apical Na permeability (PNaa) was 1.6 x 10(-6) cm/s. In CF preparations, PCla was reduced to a maximum of 2.3 x 10(-7) cm/s, whereas PNaa was increased to 6.2 x 10(-6) cm/s. The apical membrane electromotive force was -1 mV in normal and 43 mV in CF preparations. It is concluded that the method can be used to calculate Rs, apical membrane ion permeabilities, and electromotive forces from steady-state electrophysiological data.

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