Time-dependent phenomena in voltage-clamped epithelia

García-Díaz, J. Fernando; Essig, Alvin; DeLong, Joel; Civan, Mortimer M.; Schultz, Stanley G.; Thompson, Stanley R.; Hudson, Randall L.; Thomas, Sophie; Suzuki, Yuichi

doi:10.1007/bf01870663

Cited by 3 publications

(3 citation statements)

References 7 publications

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“…Our observations have important consequences not only 3DeLong and Civan (1984) and Schultz et al (1984), working with the split frog skin and Necturus urinary bladder, respectively, have presented the view that current-voltage relationships during this interval are not distorted significantly by capacitative effects. Their observations, however, do not support this claim, as we have indicated elsewhere (Garcia-Diaz and Essig, 1985).…”

Section: Resultscontrasting

confidence: 59%

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Capacitative transients in voltage-clamped epithelia

García-Díaz¹,

Essig²

1985

Biophysical Journal

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In voltage-clamped epithelia the cell membrane potential transient during a + 10-mV transepithelial pulse conforms to the expected behavior for a series combination of two linear resistance-capacitance (RC) circuits. The evolution of the cell potential is characterized by a single time constant with values of 30-130 ms in frog skin and Necturus gallbladder. These observations have important consequences for the measurement of cell membrane resistance ratios and the interpretation of current-voltage relations.

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Section: Resultscontrasting

confidence: 59%

“…for the proper measurement offR, but also for the interpretation of the I-V relations of the cell membranes. As we indicated previously (Garcia-Diaz and Essig, 1985), for epithelia where Ta << , the relation between apical voltage and cell current, Ic, at any time after the onset of the VT pulse is determined solely by Ra, i.e., AVa(t) Ail(t)…”

Section: Resultsmentioning

confidence: 57%

Capacitative transients in voltage-clamped epithelia

García-Díaz¹,

Essig²

1985

Biophysical Journal

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“…5). In principle, analysis of the brief pulses used could be obscured by capacitative transients (Garcia-Diaz & Essig, 1985). However, as previously reported (DeLong & Civan, 1984), varying the sampling time within a 31-msec period after initiating the pulses had little effect on the estimated values of P~Va and c~.…”

Section: Discussionmentioning

confidence: 95%

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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Interactions of TPA and insulin on Na+ transport across frog skin

Civan

Peterson-Yantorno

George

et al. 1989

American Journal of Physiology-Cell Physiology

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The phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) activates protein kinase C (PKC) and produces an early stimulation of Na+ transport across frog skin. The ionic basis for this stimulation was studied with combined transepithelial and intracellular electrical measurements. In an initial series of experiments, TPA approximately doubled the amiloride-sensitive short-circuit current (ISC), apical Na+ permeability (PapNa), and apical membrane conductance without affecting the basolateral membrane conductance. The apical effects led to a marked depolarization of the short-circuited skin and a small increase in intracellular Na+ concentration. TPAs increase of PapNa was sufficient to explain the stimulation of basolateral Na+ transport when both the voltage and substrate dependence of the pump were taken into account. After the early stimulation, TPA later depressed ISC. Added at this point (congruent to 1-2 h after TPA administration), insulin had no effect on ISC, whereas a partial response to vasopressin was still observed. Measured either early or late after TPA addition, the phorbol ester reduced insulin binding by congruent to 40%. Insofar as 60% of the specific binding is retained, the abolishment of insulin's natriferic response is unlikely to result from the TPA-induced reduction in hormonal binding. The data provide further support for the concept that activation of PKC produces an early stimulation of Na+ transport by increasing apical Na+ permeability, and that part of insulin's natriferic effect may be mediated by PKC activation.

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Time-dependent phenomena in voltage-clamped epithelia

Cited by 3 publications

References 7 publications

Capacitative transients in voltage-clamped epithelia

Capacitative transients in voltage-clamped epithelia

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

Interactions of TPA and insulin on Na+ transport across frog skin

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