Isolated toad skin epithelium: Transport characteristics

Rawlins, F. A.; Mateu, L.; Fragachan, F.; Whittembury, Guillermo

doi:10.1007/bf00587897

Cited by 56 publications

(32 citation statements)

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“…Rawlins et al 1970 measured the resistance profile in the isolated epithelium of toad skin with microelectrodes advanced through the inside bathing solution. The resistance recorded between the tip of a micro-electrode located within the outermost living cells (the cells of Stratum granulosum) and the inner bath was unmeasurably small with 100 mm KCl-Ringer as inner solution.…”

Section: Discussionmentioning

confidence: 99%

“…According to Rawlins et al (1970) In several tissues an electrogenic pump with r equal to about 3/2 has been demonstrated (for review see Thomas, 1972). For lack' of precise information on r for amphibian skin, r = 3/2 will be used in our calculations.…”

Section: Discussionmentioning

confidence: 99%

“…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%

“…(3) Exposure to solutions with different (Na)o must be brief enough to leave (Na)c almost unchanged. We attempted to fulfil these requirements by: (1) depolarizing the inner membranes with inner bathing solutions of high K concentration (Rawlins et al 1970);(2) blocking the Na channels with 30 gUM amiloride (Ehrlich & Crabbe, 1968;Cuthbert & Shum, 1974); and (3) using a fast-flow chamber which allows a change of the outer solution within 20 msec and reduces the unstirred layer at the outer surface of the Naselective membrane to about 15,um .…”

Section: Introductionmentioning

confidence: 99%

“…epithelium (Ussing & Windhager, 1964;Rawlins et al 1970), for instance at the apical and basal membrane of cells in the stratum granulosum. These steps will be called V. …”

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confidence: 99%

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

Fuchs

Larsen

Lindemann

1977

The Journal of Physiology

305

213

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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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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…epithelium (Ussing & Windhager, 1964;Rawlins et al 1970), for instance at the apical and basal membrane of cells in the stratum granulosum. These steps will be called V. …”

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