Relationship of Electrical Potential Differences to Net Ion Fluxes in Rat Proximal Tubules

Nature ◽  
1964 ◽  
Vol 201 (4920) ◽  
pp. 714-715 ◽  
Author(s):  
DONALD MARSH ◽  
SIDNEY SOLOMON
Keyword(s):  
Electrical Potential ◽  
Proximal Tubules ◽  
Ion Fluxes ◽  
Relationship Of

Electrophysiology of the in situ contractile vacuole complex of Paramecium reveals its membrane dynamics and electrogenic site during osmoregulatory activity.

1998 ◽  
Vol 201 (3) ◽  
pp. 451-460 ◽  
Author(s):  
T Tominaga ◽  
R D Allen ◽  
Y Naitoh
Keyword(s):  
Proton Pump ◽  
Electrical Potential ◽  
Membrane Dynamics ◽  
Contractile Vacuole ◽  
Vacuole Membrane ◽  
Input Capacitance ◽  
Linear Current ◽  
Relationship Of ◽  
Voltage Relationship

In the freshwater protozoan Paramecium multomicronucleatum, excess cytosolic water, acquired osmotically, is segregated and expelled to the cell exterior through the activity of the contractile vacuole complex. This process keeps the cell volume constant. The electrophysiological parameters of the organelle were measured in situ using a fine-tipped microelectrode inserted into the contractile vacuole, the exocytotic vesicle of the organelle to which the segregated fluid is transported before being expelled to the exterior. The input capacitance decreased markedly immediately before fluid expulsion and regained its previous value when fluid filling resumed after fluid expulsion. This change in the capacitance proved that the contractile vacuole became disconnected from its radial arms, which project from the vacuole, before fluid expulsion occurred and then reconnected with the arms after fluid expulsion. A positive electrical potential was recorded from the contractile vacuole only when it was connected to the radial arms. This implies that the electrogenic mechanism resides exclusively in the radial arms and supports the idea that the decorated spongiomes, V-type proton-pump-covered terminal tubules of the radial arms that end blindly in the cytosol, are electrogenic. The linear current­voltage relationship of the contractile vacuole membrane also implies that few voltage-activated ion channels are present in the membrane. To explain the movement of water into the contractile vacuole complex, we favour the hypothesis that the potential generated across the decorated spongiome membrane can be used to drive counter-anions from the cytosol into the lumen of the complex. The anions could then act as an osmolite to pull cytosolic water into the lumen of the organelle.

scholarly journals Electrical Potential Difference Measurements in Perfused Single Proximal Tubules of Necturus Kidney

1961 ◽  
Vol 44 (4) ◽  
pp. 679-687 ◽  
Author(s):  
Guillermo Whittembury ◽  
Erich E. Windhager
Keyword(s):  
Electrical Potential ◽  
Proximal Tubules ◽  
The Other ◽  
Potential Difference ◽  
Stopped Flow ◽  
Electrical Potential Difference ◽  
Necturus Maculosus ◽  
Other Hand ◽  
Glomerular Filtrate

Transtubular and peritubular face electrical potential differences (P.D.) of the proximal tubules of the kidney of the amphibian Necturus maculosus have been measured in situ. These measurements have been carried out both under normal conditions, when the tubular fluid originates in the glomerular filtrate, and under conditions when the composition of the tubular fluid has been altered using the stopped flow microperfusion technique. Under normal conditions the transtubular potential difference is 20 mv. (lumen-negative) and the P.D. across the peritubular face is 74 mv. (cell-negative). The P.D. across the luminal face is thus 54 mv. (cell-negative). This electrical asymmetry is not influenced by replacing the normal tubular fluid by NaCl, NaCl + mannitol, or by alteration in the intraluminal pH from 7 to 4. On the other hand, replacement of Na by K or choline and the addition of small amounts of DNP to the perfusate diminish this asymmetry.

Site of potential difference measurements in single renal proximal tubules of Necturus

1963 ◽  
Vol 204 (3) ◽  
pp. 401-404 ◽  
Author(s):  
Guillermo Whittembury
Keyword(s):  
Interstitial Fluid ◽  
Electrical Potential ◽  
Proximal Tubules ◽  
Potential Difference ◽  
Renal Proximal Tubules ◽  
Histological Sections ◽  
Necturus Maculosus ◽  
Tubular Lumen ◽  
Tip Position

The electrical potential differences from cells and lumina of the proximal tubules of the kidney of Necturus maculosus were measured with micropipette-electrodes, in vivo, and the site of measurement was permanently marked by deposition of carmine in the tissue by iontophoresis from the tip, during recording of each potential difference. The carmine deposits were subsequently localized using serial histological sections. Two negative electrical potential steps were measured, with reference to the interstitial fluid, and the tip position unequivocally marked. a) The potential difference across the peritubular face of the cell, with the microelectrode tip in the cell, averaged –70 mv (cell negative); b) the transtubular potential difference with the tip in the tubular lumen, averaged –21 mv (lumen negative).

Isolated perfused salamander proximal tubule. II. Monovalent ion replacement and rheogenic transport

1981 ◽  
Vol 241 (5) ◽  
pp. F540-F555 ◽  
Author(s):  
H. Sackin ◽  
E. L. Boulpaep
Keyword(s):  
Basolateral Membrane ◽  
Electrical Potential ◽  
Transport Current ◽  
Proximal Tubules ◽  
Ambystoma Tigrinum ◽  
Ionic Diffusion ◽  
Renal Epithelium ◽  
Monovalent Ion ◽  
Chloride Removal

Early proximal tubules of the salamander kidney (Ambystoma tigrinum) were isolated and perfused in vitro. Transepithelial and basolateral electrical potential differences, transepithelial resistances, and intracellular ionic activities were measured during removal of Na+, K+, or Cl- from the lumen, the bath, or both lumen and bath. The effects of these external ionic replacements are interpreted in terms of an equivalent circuit that represents the renal epithelium as a network of passive ionic resistances, ionic diffusion potentials, and active transport current sources. Results indicate that rheogenic transport across the basolateral membrane is substantially diminished by removal of Na+ from either lumen or bath or by removal of K+ from the bath. On the other hand, bilateral chloride removal produces an increase in transepithelial resistance but almost no change in the calculated rate of basolateral rheogenic transport. This suggests that the source of the basolateral rheogenic ion flux ia a Na-K-ATPae that actively transports an excess of outward Na+ over inward K+.

Electrolyte composition of pulmonary alveolar subphase in anesthetized rabbits

1986 ◽  
Vol 60 (3) ◽  
pp. 972-979 ◽  
Author(s):  
D. W. Nielson
Keyword(s):  
Active Transport ◽  
Electrolyte Solution ◽  
Electrical Potential ◽  
Ionic Concentration ◽  
Electrolyte Composition ◽  
Potential Difference ◽  
Ion Fluxes ◽  
Electrical Potential Difference ◽  
Aqueous Subphase ◽  
Pleural Surface

We measured the concentration of Na+, K+, Ca2+, and Cl- in the aqueous subphase of the alveolar lining by puncturing the most superficial alveoli of the exposed lungs of anesthetized rabbits with ion-selective microelectrodes and a nonselective KCl microelectrode. A buffered electrolyte solution bathed the lung surface to keep it moist and warm (38 +/- 1 degrees C) and to serve as a reference for each measurement of ionic concentration. The serum and alveolar concentrations (meq/l) were Na+ 134 +/- 6 and 135 +/- 5, K+ 3.4 +/- 0.2 and 7.3 +/- 0.7, Ca2+ 3.1 +/- 0.2 and 3.2 +/- 0.4, and Cl- 106 +/- 7 and 103 +/- 5 (mean +/- SD). Only K+ was significantly different (P less than 0.001). There was a small electrical potential difference between the alveolar lumen and the pleural surface (-3.5 +/- 0.8 mV, lumen negative) that was significantly different from zero (P less than 0.001). Although it is not possible to measure ion fluxes with these techniques, the results are consistent with active transport of one or more of the ions studied.

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