Volume changes and potential artifacts of epithelial cells of frog skin following impalement with microelectrodes filled with 3m KCl

Nelson, Deborah J.; Ehrenfeld, Jordi; Lindemann, Bernd

doi:10.1007/bf02026000

Cited by 64 publications

(28 citation statements)

References 29 publications

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“…the transient hyperpolarization, represents potential changes (independent of the absolute values), which occurred while the microelectrode position was unchanged. Regarding the magnitude of micro-electrode tip artefacts, Nelson et al (1978) observed that under the worst conditions 'pre-tippotentials' after impalement were below 5 mV for microelectrodes with resistances above 20 MQ (as in the present study).…”

Section: Discussionmentioning

confidence: 83%

Rheogenic sodium transport in a tight epithelium, the amphibian skin.

Nagel¹

1980

The Journal of Physiology

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SUMMARY1. Intracellular potentials from frog and toad skins were measured to identify rheogenic components of active Na transport across the basolateral membrane. Transcellular current flow and associated R *I-drops were blocked with amiloride or Na-free mucosal solution.2. The potential difference across the basolateral membrane was found to be hyperpolarized by 18-5 + 1*6 mV above the steady-state value immediately after blockage of apical membrane Na conductance. The hyperpolarization disappeared within 15-25 min.3. The final steady-state value of 93-1 + 2-5 mV was slightly less than reasonable estimates of the K equilibrium potential.4. The hyperpolarization could not be observed 3-5 min after addition of ouabain (10-4 M).5. Both the magnitude and duration of the hyperpolarization correlate directly with the amount of Na accumulated in the intracellular space.6. A fraction of the intracellular potential was missing when Na transport was re-established after long term blockage of apical membrane Na entry. It reappeared within 10-20 min.7. It is suggested that the hyperpolarization is due to rheogenic Na transport across the basolateral membranes. This transport mechanism may contribute some 30-50 % of the electrical gradient for passive Na entry across the mucosal membrane. 8. A coupling ratio between pumped fluxes of Na and K of about 2: 1 is calculated from the data.

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Section: Discussionmentioning

confidence: 83%

Rheogenic sodium transport in a tight epithelium, the amphibian skin.

Nagel¹

1980

The Journal of Physiology

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“…Microelectrode studies of small cells are subject to uncertainty because of the possibility of significant cell damage (Lindemann, 1975;Higgins, Gebler & Fr6mter, 1977), changes in intracellular ionic composition upon impalement (DeLong & Civan, 1978;Nelson, Ehrenfeld & Lindemann, 1978), or uncontrolled changes in electrode tip potential upon penetration of the cell membrane. Since it is difficult to exclude completely the possibility of artifacts, we considered it essential to validate our measurements by a variety of criteria.…”

Section: Justification and Validation Of The Techniquesmentioning

confidence: 99%

Intracellular ionic activities and transmembrane electrochemical potential differences in gallbladder epithelium

Reuss

Weinman

1979

J. Membrain Biol.

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Intracellular ion activities in Necturus gallbladder epithelium were measured with liquid ion-exchanger microelectrodes. Mean values for K, Cl and Na activities were 87, 35 and 22 mM, respectively. The intracellular activities of both K and Cl are above their respective equilibrium values, whereas the Na activity is far below. This indicates that K and Cl are transported uphill toward the cell interior, whereas Na is extruded against its electrochemical gradient. The epithelium transports NaCl from mucosa to serosa. From the data presented and the known Na and Cl conductances of the cell membranes, we conclude that neutral transport driven by the Na electrochemical potential difference can account for NaCl entry at the apical membrane. At the basolateral membrane, Na is actively transported. Because of the low Cl conductance of the membrane, only a small fraction of Cl transport can be explained by diffusion. These data suggest that Cl transport across the basolateral membrane is a coupled process which involves a neutral NaCl pump, downhill KCl transport, or a Cl-anion exchange system.

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“…Recent literature has pointed out that there may be significant leakage of KCl from conventional micro-electrodes filled with 3 M-KCl (Nelson, Ehrenfeld & Lindemann, 1978;Fromm & Schultz, 1981;Blatt & Slayman, 1983). This leakage may be caused by electro-diffusion of KCl from the micro-electrode, and/or by the hydrostatic pressure of the fluid column in the electrode shank.…”

Section: Micro-electrode Fabrication Andsuction Impalement Techniquementioning

confidence: 99%

Voltage clamp of bull‐frog cardiac pace‐maker cells: a quantitative analysis of potassium currents.

Giles¹,

Shibata²

1985

The Journal of Physiology

100

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5. The fully activated instantaneous current-voltage (I-V) relationship for IK is approximately linear over the range of potentials -130 to -30 mV. Thus, the ion transfer mechanism of IK may be described as a simple ohmic conductance in this range of potentials. Positive relative to -30 mV, however, the I-V exhibits significant inward rectification. W. R. GILES AND E. F. SHIBATA 8. The time course of decay of IK is a single exponential. However, the activation or onset of IK shows clear sigmoidicity in the range of potentials from the activation threshold (-40 mV) to 0 mV. This sigmoidicity may be accounted for by raising the activation variable, n, to the second power.9. The kinetics of activation and deactivation of IK are strongly modulated by potentials negative to -60 mV, but are only weak functions of potential at more positive voltages. These results strongly suggest that IK is important in triggering repolarization and in controlling the rate of development of the first part of the pace-maker potential.10. In a second series of experiments, the background K+ current in sinus venosus cells was compared and contrasted with that in adjacent atrial myocytes.11. These data show that in single cells isolated from the atrium a conventional inwardly rectifying background current exists. The size of this current is very sensitive to changes in [K+]0, it is inhibited by relatively low doses of BaCl2 (50 PLM) and it exhibits very marked inward-going rectification. It therefore is very similar to IK1 in other cardiac preparations. In contrast, similar experiments in sinus venosus cells from the same animal show conclusively that there is no detectable inwardly rectifying background K+ current in this cardiac pace-maker cell type.12. These findings are discussed in relation to three physiologically important phenomena: (1) the mechanism of repolarization of the action potential in cardiac pace-maker tissue; (2) the ionic basis of the development of the spontaneous diastolic depolarization or pace-maker potential; (3) the functionally important electrophysiological differences between pace-maker and non-pace-maker tissue.

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Volume changes and potential artifacts of epithelial cells of frog skin following impalement with microelectrodes filled with 3m KCl

Cited by 64 publications

References 29 publications

Rheogenic sodium transport in a tight epithelium, the amphibian skin.

Rheogenic sodium transport in a tight epithelium, the amphibian skin.

Intracellular ionic activities and transmembrane electrochemical potential differences in gallbladder epithelium

Voltage clamp of bull‐frog cardiac pace‐maker cells: a quantitative analysis of potassium currents.

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