Transepithelial potential difference in the proximal tubule of Necturus kidney

Edelman, A.; Anagnostopoulos, T.

doi:10.1007/bf01062277

Cited by 11 publications

(8 citation statements)

References 28 publications

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“…It should be recalled that the value of -0.8 mV is at variance with other reports on transepithelial p.d. To test whether this discrepancy is the result of some alteration of the tissue, due to the perfusion with artificial solutions, a thorough investigation was undertaken independently in the intact Necturus kidney; such experimental determinations, as well as various theoretical considerations fully support the present data (Edelman & Anagnostopoulos, 1975; also in preparation).…”

Section: Transepithelial Pdmentioning

confidence: 67%

Anion permeation in the proximal tubule ofNecturus kidney: The shunt pathway

Anagnostopoulos

1975

J. Membrain Biol.

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The effect of foreign anions on transepithelial potential difference and transepithelial input conductance was studied in the isolated perfused Necturus kidney. Two microelectrodes (recording and current-injecting) were inserted into the lumen of single proximal tubules and the peritubular perfusate was shifted reversibly for 30-60 sec from a physiologic Ringer's solution to a test solution in which chloride was replaced isosmotically by a foreign anion. The permeability sequence, obtained by potential measurements, was: lactate less than glutamate less than gluconate less than pyruvate less than benzene sulfonate less than or equal to acetate less than or equal to F less than propionate less than BrO3 less than formate less than ClO3 less than Cl than ClO4 less than I less than or equal to Br less than NO3 less than SCN. Transepithelial conductance decreased when the tissue was perfused with anions less permeable than chloride but the conductance sequence was different from the permeability sequence. Such discrepancies were more pronounced during perfusion with hyperpolarizing anions; ClO4 and I- (both more permeable than chloride) produced an important decrease in transepithelial conductance, followed by incomplete reversibility when the perfusion was shifted again to chloride Ringer's. The results are best explained by the presence of weak positive fixed charges, governing anion permeation, at the shunt pathway of the proximal tubule. An analysis of the data allows tentative estimates of shape and size of the sites.

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Section: Transepithelial Pdmentioning

confidence: 67%

Anion permeation in the proximal tubule ofNecturus kidney: The shunt pathway

Anagnostopoulos

1975

J. Membrain Biol.

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“…It is generally acknowledged that the [C1]rj[C1]e ratio is slightly higher than unity, i.e., 1.05-1.07 (Walker, Hudson, Findler & Richards 1937;Bott, 1962), when [Na]~/[-Na]v is not significantly different from 1.00 (Bott, 1962;Garland et al, 1973). The lumen has been reported to be negative with respect to interstitium by 9 to 12mV (Boulpaep, 1972;Spring & Paganelli, 1972;Spring & Kimura, 1978) or by about 1 mV (Anagnostopoulos, 1975;Edelman & Anagnostopoulos, 1976). Clearly, luminal chloride concentration appears also to be above equilibrium, in Necturus, despite a reported lack of luminal acidification (Giebisch, 1956).…”

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confidence: 99%

“…All experiments were performed in the proximal tubule of Necturus kidney, in vivo. The kidney preparation for micropuncture was described elsewhere (Anagnostopoulos, 1975;Edelman & Anagnostopoulos, 1976). …”

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confidence: 99%

Chloride distribution in the proximal convoluted tubule ofNecturus kidney

1981

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To assess the mechanism(s) by which intraluminal chloride concentration is raised above equilibrium values, intracellular Cl- activity (alpha iCl) was studied in the proximal tubule of Necturus kidney. Paired measurements of cell membrane PD (VBL) and Cl-selective electrode PD (VBLCl) were performed in single tubules, during reversible shifts of peritubular or luminal fluid composition. Steady-state alpha iCl was estimated at 14.6 +/- 0.6 mmol/liter, a figure substantially higher than that predicted for passive distribution. To determine the site of the uphill Cl- transport into the cell, an inhibitor of anion transport (SITS) was added to the perfusion fluid. Introduction of SITS in peritubular perfusate decreased alpha iCl, whereas addition of the drug in luminal fluid slightly increased alpha iCl; both results are consistent with basolateral membrane uphill Cl- transport from interstitium to the cell. TMA+ for Na+ substitutions in either luminal or peritubular perfusate had no effect on alpha iCl. Removal of bicarbonate from peritubular fluid, at constant pH (a situation increasing HCO3- outflux), resulted in an increase of alpha iCl, presumably related to enhanced Cl- cell influx: we infer that Cl- is exchanged against HCO3- at the basolateral membrane. The following mechanism is suggested to account for the rise in luminal Cl- concentration above equilibrium values: intracellular CO2 hydration gives rise to cell HCO3- concentrations above equilibrium. The passive exit of HCO3- at the basolateral membrane energizes an uphill entry of Cl- into the cell. The resulting increase of alpha iCl, above equilibrium, generates downhill Cl- diffusion from cell to lumen. As a result, luminal Cl- concentration also increases.

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“…By comparison, membrane p.d. in vivo has been found to be between -70 and -75 mV (Whittembury, Sugino & Solomon, 1961;Khuri et al 1972;Boulpaep, 1972;Edelman & Anagnostopoulos, 1976 …”

Section: Resultsmentioning

confidence: 99%