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

Leibowich, Shlomo; DeLong, Joel; Civan, Mortimer M.

doi:10.1007/bf01870450

Cited by 16 publications

(10 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…With serosat gluconate, studied by us in whole skins, effects were insignificant or minimal, despite marked cell depolarization. Leibowich et al (1988) have reported similar findings in whole skins; in isolated epithelia, on the other hand, serosal gluconate regularly inhibited the short-circuit current. On the basis of analysis of the apical amiloride-sensitive currentvoltage relationship, it was concluded that serosal gluconate does not inhibit either apical Na permeability or the basolateral Na pump, but likely reduces cell volume, triggering inhibition of basolateral K channels.…”

Section: Discussionsupporting

confidence: 68%

“…Other substitution experiments have pointed to basolateral NaCI cotransport (Ferreira & Ferreira, 1981;Giraldez & Ferreira, 1984;D6rge et al, 1985), whereas studies of volume regulation have suggested basolateral NaKC12 cotransport (Ussing, 1985). On the other hand, isotope kinetic studies of Stoddard, Jakobsson and Helman (1985) have indicated electroneutral basolateral CI transport, for the most part uncoupled to transport of either Na or K. Cellular electrical effects of serosal CI removal have been described by Biber et al (1985), by Duffy et al (1986), and by Leibowich, DeLong and Civan (1988), Our findings provide additional information concerning membrane electrophysiology and cell cation activities.…”

Section: Discussionmentioning

confidence: 93%

See 1 more Smart Citation

Influence of serosal Cl on transport properties and cation activities in frog skin

Klemperer

Essig

1988

J. Membrain Biol.

View full text Add to dashboard Cite

The effects of serosal substitution of isosmotic Na2SO4-Ringer solution for NaCl-Ringer solution were studied in the short-circuited frog skin (Rana pipiens, Northern variety). Despite prompt changes of transepithelial measurements, initial cellular effects were slight. After 30 to 45 min, however, the transcellular current had decreased and the cell electrical potential had depolarized, in association with decrease of the apical membrane fractional resistance and basolateral membrane conductance. Apical membrane slope conductance was unaffected. Similar effects were obtained with isolated epithelia. With the use of gluconate or NO3 in place of Cl, the effects on cellular current and conductance were minimal or insignificant, despite changes of the cell potential, fractional resistance, and basolateral conductance similar to those seen with sulfate. Following prolonged exposure to serosal SO4-Ringer, the extent of depolarization induced by raising the serosal K concentration decreased, indicating diminution of basolateral K conductance and the existence of other basolateral conductances. Equilibration in serosal gluconate-Ringer enhanced polarization on serosal restoration of Cl or removal of Na, again indicating a time-dependent change in the basolateral conductance pattern. Depolarization on removal of serosal Cl was not attributable to inhibition of the pump. Nor was it the result of decrease of the K equilibrium potential EK: exposure to serosal SO4-Ringer decreased cell K activity aKc from 104 +/- 6 to 58 +/- 4 mM (n = 5), but EK was reduced only slightly; exposure to serosal gluconate increased aKc and EK. Serosal sulfate lowered the cell Na activity aNac, but the electrochemical potential difference for Na across the apical surface was unaffected. The concurrent decrease of both aKc and aNac following serosal substitution of SO4 for Cl raises questions concerning mechanisms of osmoregulation.

show abstract

Section: Discussionsupporting

confidence: 68%

Section: Discussionmentioning

confidence: 93%

Influence of serosal Cl on transport properties and cation activities in frog skin

Klemperer

Essig

1988

J. Membrain Biol.

View full text Add to dashboard Cite

show abstract

“…Effects of serosal tonicity and Cl" re placements on transepithelial Na+ transport have been the subject of several studies [7][8][9][10]. Microelectrode experiments [7][8][9] showed that a major part of the inhibition on Na+ transport following Cl" removal or after elevation of the serosal osmolality could be attributed to cell depolarization. This depo larization of the intracellular potential was found to be caused by a reduction of the basolateral K+ conductance.…”

Section: Introductionmentioning

confidence: 99%

Effects of Serosal Hypotonicity and Anion Substitutions on Apical and Basolateral K<sup>+</sup> Conductances

Deynse¹,

Driessche²

1992

Cell Physiol Biochem

View full text Add to dashboard Cite

The present study was performed to investigate effects of volume changes induced by serosal hypotonicity and anion replacements on K⁺ movements through frog skin (Rana temporaria). The apical K⁺ conductance was investigated with noise analysis and microelectrode recordings. In all experiments, the transepithelial K⁺ currents recorded under short-circuit conditions (I_sc) were driven by a K⁺ gradient oriented from mucosa to serosa. In control conditions, the major anion was gluconate in both bathing solutions. Replacement of serosal gluconate by chloride augmented I_scfrom 5.1 to 24 µA/cm². Reduction of serosal osmolality from 231 to 124 mosm/kg elicited an increase of I_sc from 8.1 to 31 µA/cm². Control as well as activated currents were inhibited by millimolar concentrations of mucosal Ba²⁺, which shows that I_sc is carried by K⁺. Single-channel currents (i) and channel densities (M) were obtained from the analysis of Ba²⁺-induced noise. The serosal anion replacement increased i from 2.0 to 3.6 pA, whereas serosal hypotonicity augmented i from 1.1 to 3.2 pA. In addition, serosal gluconate-Cl^– replacement elicited an increase of M from 3.6 to 9.7 µm^–2, while a reduction of the osmolality had no effect on M. Anion replacements in the mucosal bathing media were without any major effect. Microelectrode experiments showed that the serosal gluconate-Cl^- replacement as well as the reduction of the tonicity caused hyperpolarizations of the cell interior from –15 to –27 mV and from –32 to –44 mV, respectively. Concomitantly, the fractional resistance increased from 26 to 32% and from 57 to 79%. Our data demonstrate that volume expansion caused by serosal hypotonicity elevates transepithelial K⁺ currents exclusively by increasing basolateral K⁺ conductance. On the other hand, serosal gluconate-Cl^– replacements elicited an additional augmentation of the apical K⁺ conductance. The latter result could be caused by more pronounced volume increases or by effects of serosal Cl^– on cellular mediators of the apical pathway.

show abstract

“…The baseline pulsing was periodically interrupted to impose a sequence of voltage pulses across the skin. Each train comprised 12 pairs of alternately hyperpolarizing and depolarizing pulses, the magnitude increasing by 20 mV in successive steps (DeLong & Civan, 1984;Leibowich, DeLong & Civan, 1988). Data were acquired with pulse durations of 16 or 32 msec and interpulse intervals of 240-640 msec, but the choice of pulse duration is not critical (Civan et al, 1989).…”

Section: Intracellular Measurementsmentioning

confidence: 99%

“…Insofar as Cd =+ is thought to reduce the apical C1-conductance of frog skin (Hayashi et al, 1977), these experiments were performed with skins bathed with the standard Ringer's solution on their serosal surfaces, but with an equimolar replacement of NO3 for Clon their mucosal surfaces. This approach has been empirically used in studies of frog skin to reduce the baseline, non-Na + conductance (Nagel, GarciaDiaz & Essig, 1983;Civan et al, 1987;Leibowich et al, 1988).…”

Section: Approaches For Altering Cytosolic Activity Of Ca 2+mentioning

confidence: 99%

Ca2+-independent form of protein kinase C may regulate Na+ transport across frog skin

et al. 1991

Self Cite

View full text Add to dashboard Cite

Activators of protein kinase C (PKC) stimulate Na+ transport (JNa) across frog skin. We have examined the effect of Ca2+ on PKC stimulation of JNa. Both the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) and the diacyl-glycerol sn-1,2-dioctanoylglycerol (DiC8) were used as PKC activators. Blocking Ca2+ entry into the cytosol (either from external or internal stores) reduced the subsequent natriferic effect of the PKC activators. This negative interaction did not simply reflect saturation of activation of the apical Na+ channels, since the stimulations produced by blocking Ca2+ entry and adding cyclic AMP were simply additive. The Ca2+ dependence of the natriferic effect could have reflected either a direct action of cytosolic Ca2+ on PKC or an indirect action on the final receptor site (the Na+ channel). To distinguish between these possibilities, the TPA- and phospholipid-dependent kinase activity of broken-cell preparations was assayed. The kinase activity was not stimulated by physiological levels of Ca2+, and in fact was inhibited at millimolar concentrations of Ca2+. We conclude that the effects of Ca2+ on the natriferic response to PKC activators are indirect. Reducing cytosolic uptake of Ca2+ may have stimulated Na+ transport by a chemical modification of the apical channels observed in other tight epithelia. The usual stimulation of Na+ transport produced by PKC activators in frog skin may reflect the operation of a nonconventional form of PKC. This enzyme is Ca2+ independent and seems related to the nPKC or PKC epsilon observed in other systems.

show abstract

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

Cited by 16 publications

References 30 publications

Influence of serosal Cl on transport properties and cation activities in frog skin

Influence of serosal Cl on transport properties and cation activities in frog skin

Effects of Serosal Hypotonicity and Anion Substitutions on Apical and Basolateral K<sup>+</sup> Conductances

Ca2+-independent form of protein kinase C may regulate Na+ transport across frog skin

Contact Info

Product

Resources

About