The intracellular electrical potential profile of the frog skin epithelium

Nagel, Wolfram

doi:10.1007/bf01067010

Cited by 115 publications

(68 citation statements)

References 16 publications

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“…The experiments were done on isolated abdominal skins from Rana temporaria, R. esculenta, and Bufo marinru8 with micro-electrode techniques as described previously (Nagel, 1976a(Nagel, , 1977a(Nagel, , 1978a. The skins were mounted horizontally and supported by a copper grid on the serosal side in a special Ussing-type chamber, which was open at the upper side for access of the micro-electrode.…”

Section: Methodsmentioning

confidence: 99%

“…Measurement of intracellular potentials is possible from frog skin epithelium for rather extended periods of time (Nagel, 1976a(Nagel, , 1977a(Nagel, , 1978aHelman & Fisher, 1977). From previous measurements it was already suggested, that rheogenic Na transport might contribute to the intracellular potential of the frog skin epithelium (Nagel, 1976a;Nagel & Helman, 1977). It will be shown, that a considerable fraction of the basolateral membrane potential is directly generated by the Na pump under conditions of normal transport.…”

Section: Introductionmentioning

confidence: 99%

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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: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Nagel¹

1980

The Journal of Physiology

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“…Membrane potentials of the outward facing membrane have been recorded with micro-electrodes (e.g. Ussing & Windhager, 1964;Rawlins, Mateu, Fragachan & Whittembury, 1970;Hviid Larsen, 1973;Nagel, 1976; see also Ehrenfeld, Nelson & Lindemann, 1976), but the Na activity (Na)c of the transporting cells was unknown under all experimental conditions. Direct measurements with Na-selective micro-electrodes (Janacek, Morel & Bourguet, 1968) are technically difficult and include a risk of diffusional Na leakage through the puncture channel (Lindemann, 1975).…”

Section: Introductionmentioning

confidence: 99%

Current—voltage curve of sodium channels and concentration dependence of sodium permeability in frog skin

Fuchs

Larsen

Lindemann

1977

The Journal of Physiology

310

215

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SUMMARY1. The inward facing membranes of in vitro frog skin epithelium were depolarized with solutions of high K concentration. The electrical properties of the epithelium are then expected to be governed by the outward facing, Na-selective membrane.2. In this state, the transepithelial voltage (V) was clamped to zero and step-changes of Na activity in the outer solution ((Na)o) were performed with a fast-flow chamber at constant ionic strength, while the shortcircuit current was recorded.3. At pre-selected times after a step-change of (Na)o the current response (I) to a fast voltage staircase was recorded. This procedure was repeated after blocking the Na channels with amiloride to obtain the current-voltage curve of transmembrane and paracellular shunt pathways. The current-voltage curve of the Na channels was computed by subtracting the shunt current from the total current. 4. The instantaneous INa,-V curve thus obtained at a given (Na)0 could easily be fitted with the constant field equation in the range between -50 and zero mV. This fit yielded approximate estimates of PNa, the Napermeability of the Na-selective membrane (at this (Na)0) and the cellular Na activity, (Na),. As residual properties of the serosal membrane were ignored the computed values are expected to underestimate the true ones.5. At constant (Na)c, the steady-state value of 1/PNa increases linearly with (Na)o. Error analysis and the effect of drugs show that the dependence is not due to the residual properties of the inward facing membranes but reflects the true behaviour of PNa.6. The steady-state PNa at a given (Na)o is smaller than the transient PNa observed right after a stepwise increase of (Na)o to this value. The time constant of PNa-relaxation is in the order of seconds.138 W. FUCHS, E. HVIID LARSEN AND B. LINDEMANN 7. In conclusion, Na transport through open Na-selective channels of the outward facing membrane of the stratum granulosum cells can be described as an electrodiffusion process which as such does not saturate with increasing (Na)0. However, when added to the outer border of the membrane Na causes a decrease of PNa within several seconds. It is considered that binding of Na results in closure of Na channels.

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“…Cell chloride concentration is normally Ussing, 1961] which is much more than required for elec trochemical equilibrium with the inside bath. Thus, the potential difference (PD) between cell interior and inside bath is normally between 80 and 100 mV [Nagel, 1976;Niel sen. 1985], Since the potassium channels o f the basolateral membrane are already open, the activation o f chloride channels leads to loss of KC1. This process continues until all cell chloride is lost.…”

Section: Mediummentioning

confidence: 99%

Epithelial Cell Volume Regulation Illustrated by Experiments in Frog Skin

Ussing¹

1986

Kidney Blood Press Res

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The volume control of the syncytium of principal cells (as opposed to the mitochondria-rich cells) is largely confined to the movement of ions and water through the basolateral membrane. The apical membrane is nearly tight to water and ions except sodium. The basolateral membrane is normally tight to chloride, but its chloride channels open if the cells swell osmotically or if the membrane is depolarized. If the epithelium has lost KC1 during osmotic swelling, it is recovered by a basolateral cotransport of KNaCl₂

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The intracellular electrical potential profile of the frog skin epithelium

Cited by 115 publications

References 16 publications

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

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

Current—voltage curve of sodium channels and concentration dependence of sodium permeability in frog skin

Epithelial Cell Volume Regulation Illustrated by Experiments in Frog Skin

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