Relationship of transient electrical properties to active sodium transport by toad urinary bladder

Weinstein, Frank C.; Rosowski, John J.; Peterson, Kim; Delalic, Zdenka; Civan, Mortimer M.

doi:10.1007/bf01869003

Cited by 20 publications

(18 citation statements)

References 48 publications

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“…Furthermore, the asymmetrical transient responses of transepithelial current-to-voltage pulses sometimes observed (Fig. 1) has suggested that some of the time-dependent changes may reflect polarization effects noted with longer pulses (Weinstein et al, 1980), and not solely reflect capacitative transients. In studying the effects of CI-on Na + transport, we have therefore chosen to use voltage pulses of 16-to 32-msec duration.…”

Section: Discussionmentioning

confidence: 98%

“…Step changes in transepithelial voltage or current can result in time-dependent changes in the conju- gate parameter, which are not ascribable to simple capacitative responses (Weinstein et al, 1980). At least some of these time-dependent effects likely reflect polarization potentials and impedances resulting from ionic translocations during prolonged stimulation.…”

Section: Measurements Of P~amentioning

confidence: 98%

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Apical Na+ permeability of frog skin during serosal Cl− replacement

1988

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Gluconate substitution for serosal Cl- reduces the transepithelial short-circuit current (Isc) and depolarizes short-circuited frog skins. These effects could result either from inhibition of basolateral K+ conductance, or from two actions to inhibit both apical Na+ permeability (PapNa) and basolateral pump activity. We have addressed this question by studying whole-and split-thickness frog skins. Intracellular Na+ concentration (CcNa) and PapNa have been monitored by measuring the current-voltage relationship for apical Na+ entry. This analysis was conducted by applying trains of voltage pulses, with pulse durations of 16 to 32 msec. Estimates of PapNa and CcNa were not detectably dependent on pulse duration over the range 16 to 80 msec. Serosal Cl- replacement uniformly depolarized short-circuited tissues. The depolarization was associated with inhibition of Isc across each split skin, but only occasionally across the whole-thickness preparations. This difference may reflect the better ionic exchange between the bulk medium and the extracellular fluid in contact with the basolateral membranes, following removal of the underlying dermis in the split-skin preparations. PapNa was either unchanged or increased, and CcNa either unchanged or reduced after the anionic replacement. These data are incompatible with the concept that serosal Cl- replacement inhibits PapNa and Na,K-pump activity. Gluconate substitution likely reduces cell volume, triggering inhibition of the basolateral K+ channels, consistent with the data and conclusions of S.A. Lewis, A.G. Butt, M.J. Bowler, J.P. Leader and A.D.C. Macknight (J. Membrane Biol. 83:119-137, 1985) for toad bladder. The resulting depolarization reduces the electrical force favoring apical Na+ entry. The volume-conductance coupling serves to conserve volume by reducing K+ solute loss. Its molecular basis remains to be identified.

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Section: Discussionmentioning

confidence: 98%

Section: Measurements Of P~amentioning

confidence: 98%

Apical Na+ permeability of frog skin during serosal Cl− replacement

1988

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“…This concept is supported by the reports that: (i) Sufficient intracellular sodium is accumulated during potassium depletion of toad bladder epithelium to support such exchange . (ii) Negative feedback between intracellular sodium activity a~ and apical sodium permeability (P~) could provide the basis for the reduced apical sodium entry following potassium depletion (Erlij & Smith, 1973;Lewis, Eaton & Diamond, 1976;Cuthbert & Shum, 1977;Turnheim, Frizzell & Schultz, 1978;Weinstein et al, 1980;Chase & A1-Awqati, 1979); this feedback may be mediated by changes in intracellular calcium activity (Blaustein, 1974;Grinstein & Erlij, 1978;Taylor & Windhager, 1979;Lee, Taylor & Windhager, 1980;Chase & A1-Awqati, 1981), and (iii) Computer simulation has permitted qualitative replication of the time-lag phenomenon, once the feedback between a~a and P~P, is introduced into the model (Civan & Bookman, 1982). Since these pieces of evidence are indirect, a more direct testing of the thesis was attempted in the present work.…”

Section: Discussionmentioning

confidence: 99%

Microelectrode study of K+ accumulation by tight epithelia: II. Effect of inhibiting transepithelial Na+ transport on reaccumulation following depletion

DeLong

Civan

1983

J. Membrain Biol.

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The effects of restoring serosal potassium to potassium-depleted toad urinary bladders have been re-examined using double-barrelled microelectrodes. The data confirm the existence of a time-lag phenomenon, a dissociation between potassium reaccumulation and restoration of short-circuit current. Returning serosal potassium stimulates an increase in intracellular potassium activity 21-26 min before any increase can be detected in short-circuit current. The reaccumulation of potassium has been further studied using split frog skin, a far more suitable preparation for electrophysiologic study than toad bladder. Under baseline short-circuited conditions, potassium is accumulated against an electrochemical gradient of 22 +/- 4 mV. Reaccumulation of potassium by potassium-depleted tissues can be blocked by inhibiting the Na,K-exchange pump with high concentrations of ouabain. On the other hand, blocking apical sodium entry by the addition of 10(-4) M amiloride to the outer bathing medium does not interfere with reaccumulation of potassium. The data support the concept that the time-lag phenomenon of toad bladder reflects stimulation of potassium reaccumulation by the sodium pump in exchange for the extrusion of excess cell sodium collected during the period of potassium depletion. This reaccumulation of potassium can proceed before the entry of significant added amounts of sodium across the apical plasma membrane.

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“…Since transients occur in the absence of Cl-in the bathing media (isethionate as substitute, Weinstein et al 1980; gluconate as substitute, personal observation), process B appears not to involve Cl-currents. Thus changes in the basolateral K+ conductance appear to offer the best explanation for the transient phenomenon.…”

Section: Discussionmentioning

confidence: 99%

Transient electrical phenomenon of the voltage‐clamped toad urinary bladder.

Gordon

1990

The Journal of Physiology

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SUMMARY1. The effects of changes in voltage on the transepithelial current through the toad urinary bladder have been studied using Ussing chambers.2.Step changes in voltage produced two transient currents of duration seconds and minutes respectively.3. Amiloride, which was used to block all active transport, also eliminated the transient nature of the current responses, indicating that the phenomena were cellular in origin. In the presence of amiloride, amphotericin B regenerated the shortcircuit current and the transient behaviour.4. The effects of substituting gluconate for Cl-in the medium were examined.Similar transient responses were observed, indicating that they were not due to changes in a plasma membrane Cl-conductance. 5. The shape and magnitude of the first current transient changed with (i) changes in the mucosal Na+ concentration, (ii) the magnitude of the transepithelial voltage step, (iii) the addition of antidiuretic hormone, (iv) changes in the serosal K+ concentration, or (v) the addition of ouabain.6. The second current transient was similarly affected by such challenges. 7. In some bladders the voltage step produced current oscillations similar to those obtained after the epithelium had been challenged with a serosal osmotic step (Gordon, 1988).8. The results suggest that two major processes are initiated by a transepithelial voltage step. The first involves a change in the K+ conductance of the basolateral membrane and the second is associated with the alteration of cellular ion content and Na+ pump rate.

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Relationship of transient electrical properties to active sodium transport by toad urinary bladder

Cited by 20 publications

References 48 publications

Apical Na+ permeability of frog skin during serosal Cl− replacement

Apical Na+ permeability of frog skin during serosal Cl− replacement

Microelectrode study of K+ accumulation by tight epithelia: II. Effect of inhibiting transepithelial Na+ transport on reaccumulation following depletion

Transient electrical phenomenon of the voltage‐clamped toad urinary bladder.

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