Current-induced voltage transients inNecturus proximal tubule

Spring, Kenneth R.

doi:10.1007/bf01868234

Cited by 21 publications

(15 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Peritubular and transepithelial PDs agree well with previously published values [3,8,13,14,16,17]. Reduction of the luminal NaC1 concentration to 55 mM had no effect on peritubular PD or cell C1 activity.…”

Section: Chloride Ringer's Experimentssupporting

confidence: 91%

“…Since we did not systematically check the tip potential of all the voltage electrodes, we did not correct transepithelial PDs for changes in tip potential. For the potential dependence experiments an axial electrode [13] was inserted into the lumen of a free f/ow tubule. Constant current pulses were injected across the tubular epithelium using triangular waves generated by a function generator (Model FG101, Tektronix, Beaverton, Oreg.…”

Section: Electrical Methodsmentioning

confidence: 99%

“…It was possible, by using a slow symmetrical triangular wave, to pass relatively large currents across the epithelium and thereby change the transepithelial PD by 50 to 70 mV without creating polarization potentials. Only a small fraction of the transepithelial current flows through the cells [13], and the change in peritubular PD is much smaller than the change in luminal PD (i.e., ca. 10 mV).…”

Section: Potential Dependence Experimentsmentioning

confidence: 99%

See 2 more Smart Citations

Chloride reabsorption by renal proximal tubules of necturus

1978

Self Cite

View full text Add to dashboard Cite

Summary. Movement of C1 from the lumen of Necturus proximal tubule into the cells is mediated and dependent on the presence of luminal Na. Intracellular C1 activity was monitored with ion selective microelectrodes. In C1 Ringer's perfused kidneys, cell C1 activity was 24.5_+ 1.1 mM, 2 to 3 times higher than that predicted for passive distribution. When luminal NaC1 was partially replaced by mannitol (capillaries perfused with C1 Ringer's) cell C1 decreased showing a sigmoidal dependence on luminal NaC1. Peritubular membrane potential was unaltered. Sulfate Ringer's perfusion of the kidneys washed out all cell C1 but did not alter peritubular membrane potential. Chloride did not enter the cell when the tubule lumen was perfused with 100 mM KC1, LiC1, or tetramethylammonium C1. Luminal perfusion of NaC1 caused cell CI to rise rapidly to the same value as the controls in the C1 Ringer's experiments. Perfusion of the tubule lumen with mixtures of NaC1 and NazSO~, while the capillaries contained sulfate Ringer's yielded a sigmoidal dependence of cell C1 on luminal NaC1 activity. Chloride movement from the lumen into the proximal tubule cells required approximately equal concentrations of Na and C1. Current clamp experiments indicated that intracellular chloride activity was insensitive to alterations in luminal membrane potential, suggesting that chloride entry was electrically neutral. The transcellular chloride flux was calculated to constitute about one half of the normal chloride reabsorption rate. We conclude that the cell C1 activity is primarily determined by the NaC1 concentration in the tubule lumen and that C1 entry across the luminal membrane is mediated.Reabsorption of chloride by the Necturus proximal tubule has been explained on the basis of passive driving forces. The transepithelial potential difference (PD), oriented lumen negative, of 10 to 15 mV is thought to provide sufficient driving force to move chloride across the permeable extracellular shunt pathway [5,6, 17,18]. However, the ratio of the chloride concentration in the tubule lumen to that of the plasma is always near 1.0, which does not agree with the value predicted from the transepithelial PD for a passively distributed ion [2,6,8]. In addition, intracellular chloride activity in Necturus proximal tubule cells is about

show abstract

Section: Chloride Ringer's Experimentssupporting

confidence: 91%

Section: Electrical Methodsmentioning

confidence: 99%

Section: Potential Dependence Experimentsmentioning

confidence: 99%

See 1 more Smart Citation

Chloride reabsorption by renal proximal tubules of necturus

1978

Self Cite

View full text Add to dashboard Cite

show abstract

“…Values for all transport parameters of the shunt path and epithelium were calculated and compared with available experimental evidence. Volume flow and electric currents predicted by the model compared favorably with experimental observations.A new model for the renal proximal tubule is presented in an attempt to explain the results of the preceeding paper [34]. The proximal tubule is represented as a parallel path system in which one path (the extracellular) is composed of barriers in series.…”

mentioning

confidence: 99%

A parallel path model forNecturus proximal tubule

Spring

1973

J. Membrain Biol.

Self Cite

View full text Add to dashboard Cite

Summary. A parallel path model based on the principles of nonequilibrium thermodynamics was developed for the Necturus proximal tubule. The cellular path was represented as a luminal membrane followed by an irreversible active NaC1 transport system in the peritubular barrier. The shunt pathway was described as three "coarse"' barriers in series: tight junction, lateral intercellular spaces, and basement membrane with connective tissue. Volume and solute flows were predicted by the model equations as a function of applied electric current. Variations of the model parameters revealed the quantitative importance of the shunt path properties and the relative insensitivity of epithelial transport to changes in most cell parameters. Circulation of electric current and solute within the epithelium were shown to significantly influence the bahavior of the tubule in the presence of an electric field. Values for all transport parameters of the shunt path and epithelium were calculated and compared with available experimental evidence. Volume flow and electric currents predicted by the model compared favorably with experimental observations.A new model for the renal proximal tubule is presented in an attempt to explain the results of the preceeding paper [34]. The proximal tubule is represented as a parallel path system in which one path (the extracellular) is composed of barriers in series. Previous investigators have suggested the possibility of fluid and ion flows through the tight junctions and extracellular shunt path. Bentzel et al. [8] proposed a tight junction path in parallel with the cell luminal membrane on the basis of fluid conductance and anatomical measurements. Boulpaep [ 11 ] put forth an analogous concept for ion permeation based on electrical measurements of the relative resistance of the epithelium and individual cell membranes. Many authors have since emphasized the importance of the extracellular shunt path in determining epithelial properties [13, 18 -20, 29, 31, 45]. Models for such a parallel path system in the rat ileum [14] and gallbladder [3] were not in a form in which my results could be evaluated. The model presented here is a specific application of the

show abstract

“…The question has naturally arisen whether the flow of NaC1, of water, or of both, across the tight junction might be responsive to the transtubular hydrostatic pressure difference. The results of several studies imply rather strongly that reduction of the transtubular hydrostatic pressure difference leads to dilatation of the intercellular channels [3,11,17,27,30]. Although it is easy to understand how this pressure difference might affect the extent of dilatation of the channels, it is less clear how flow processes at the tight junction might be influenced.…”

Section: Subscriptsmentioning

confidence: 92%

A model of NaCl and water flow through paracellular pathways of renal proximal tubules

Huß

Marsh

1975

J. Membrain Biol.

View full text Add to dashboard Cite

To explain how hydrostatic pressure differences between tubule lumen and interstitium modulate isotonic reabsorption rates, we developed a model of NaCl and water flow through paracellular pathways of the proximal tubule. Structural elements of the model are a tight junction membrane, an intercellular channel whose walls transport NaCl actively at a constant rate, and a basement membrane. Equations of change were derived for the channel, boundary conditions were formulated from irreversible thermodynamics, and a pressure-area relationship typical of thin-walled tubing was assumed. The boundary value problem was solved numerically. The principal conclusions are: 1) channel NaCl concentration must remain within a few mOsm of isotonic values for reabsorption rates to be modulated by transtubular pressure differences known to affect this system: 2) basement membrane and channel wall parameters determine reabsorbate tonicity; tight junction parameters affect the sensitivity of reabsorption to transmural pressure; 3) channel NaCl concentration varies inversely with transmural pressure difference; this concentration variation controls NaCl diffusion through the tight junction; 4) modulation of NaCl diffusion through the tight junction controls the rate of isotonic reabsorption; modulation of water flow can increase sensitivity to transmural pressure; 5) no pressure-induced change in permeability of the tight junction or basement membrane is needed for pressure to modulate reabsorption; and 6) system performance is indifferent to the distribution of active transport sites, to the numerical value of the compliance function, and to the relationship between lumen and cell pressures.

show abstract

Current-induced voltage transients inNecturus proximal tubule

Cited by 21 publications

References 18 publications

Chloride reabsorption by renal proximal tubules of necturus

Chloride reabsorption by renal proximal tubules of necturus

A parallel path model forNecturus proximal tubule

A model of NaCl and water flow through paracellular pathways of renal proximal tubules

Contact Info

Product

Resources

About