Intracellular chloride activity of rabbit proximal straight tubule perfused in vitro

1988 ◽  
Vol 255 (1) ◽  
pp. F49-F56 ◽  
Author(s):  
K. Ishibashi ◽  
S. Sasaki ◽  
N. Yoshiyama
Keyword(s):  
Basolateral Membrane ◽  
Proximal Tubule Cell ◽  
Tubule Cell ◽  
Cl Transport ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Intracellular Chloride Activity ◽  
Chloride Activity ◽  
Basolateral Membrane Potential

To examine the cellular mechanism of Cl- transport in the proximal tubule, cell Cl- activity (aiCl) was measured with double-barreled Cl(-)-selective microelectrodes in the rabbit proximal straight tubules (PST) perfused in vitro. When tubules were perfused and bathed with ultrafiltrate-like solution, aiCl (corrected for the interference from undetermined intracellular anions, 4.2 mM) was 17.8 +/- 0.5 mM (n = 90), and this value was 1.3 times higher than that predicted from passive distribution (basolateral membrane potential, Vbl = -51.9 +/- 0.8 mV). Reducing either luminal or bath Cl- indicated that the basolateral membrane plays a more important role as a determinant of aiCl. aiCl reduction rates induced by luminal Cl- removal was inhibited by 75% by 1 mM SITS added to the lumen but was not inhibited by furosemide (0.1 mM). Application of SITS in the lumen in the control condition, however, did not change aiCl appreciably. Reducing the luminal HCO3- from 25 to 5 mM did not significantly change aiCl or Vbl. Replacing luminal Na+ with choline decreased aiCl but these effects were still present when luminal Cl- was absent. We conclude that in the rabbit PST: 1) Cl- is taken up into the cell against the electrochemical gradient, 2) the basolateral membrane plays a more important role in the regulation of aiCl, and 3) luminal Cl- transport is SITS sensitive and Na+ independent.

Mechanism of bicarbonate exit across basolateral membrane of rabbit proximal straight tubule

1987 ◽  
Vol 252 (1) ◽  
pp. F11-F18 ◽  
Author(s):  
S. Sasaki ◽  
T. Shiigai ◽  
N. Yoshiyama ◽  
J. Takeuchi
Keyword(s):  
Negative Charge ◽  
Driving Forces ◽  
Basolateral Membrane ◽  
Disulfonic Acid ◽  
Exit Mechanism ◽  
Total Replacement ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Basolateral Membrane Potential

To clarify the mechanism(s) of HCO3- (or related base) transport across the basolateral membrane, rabbit proximal straight tubules were perfused in vitro, and intracellular pH (pHi) and Na+ activity (aiNa) were measured by double-barreled ion-selective microelectrodes. Lowering bath HCO3- from 25 to 5 mM at constant PCO2 depolarized basolateral membrane potential (Vbl), and reduced pHi. Most of these changes were inhibited by adding 1 mM 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) to the bath. Total replacement of bath Na+ with choline also depolarized Vbl and reduced pHi, and these changes were also inhibited by SITS. Reduction in aiNa was observed when bath HCO3- was lowered. Taken together, these findings suggest that HCO3- exists the basolateral membrane with Na+ and negative charge. Calculation of the electrochemical driving forces suggests that the stoichiometry of HCO3-/Na+ must be larger than two for maintaining HCO3- efflux. Total replacement of bath Cl- with isethionate depolarized Vbl gradually and increased pHi slightly, implying the existence of a Cl(-)-related HCO3- exit mechanism. The rate of decrease in pHi induced by lowering bath HCO3- was slightly reduced (20%) by the absence of bath Cl-. Therefore, the importance of Cl(-)-related HCO3- transport is small relative to total basolateral HCO3- exit. Accordingly, these data suggest that most of HCO3- exits the basolateral membrane through the rheogenic Na+/HCO3- cotransport mechanism with a stoichiometry of HCO3-/Na+ of more than two.

scholarly journals Maturation of rabbit proximal straight tubule chloride/base exchange

1998 ◽  
Vol 274 (5) ◽  
pp. F883-F888 ◽  
Author(s):  
Mehul Shah ◽  
Raymond Quigley ◽  
Michel Baum
Keyword(s):  
Adult Rabbit ◽  
Albumin Solution ◽  
Nacl Transport ◽  
Base Exchange ◽  
Straight Tubule ◽  
Volume Absorption ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Proximal Tubular

The present in vitro microperfusion study compared the mechanism and rates of NaCl transport in neonatal and adult rabbit proximal straight tubules. In proximal straight tubules perfused with a late proximal tubular fluid and bathed in a serumlike albumin solution, the rate of volume absorption ( J V) was 0.54 ± 0.10 and 0.12 ± 0.05 nl ⋅ mm−1 ⋅ min−1in adults and neonates, respectively ( P < 0.05). With the addition of 10−5 M bath ouabain, J Vdecreased to 0.27 ± 0.07 and −0.03 ± 0.04 nl ⋅ mm−1 ⋅ min−1in adult and neonatal tubules, respectively ( P < 0.05), consistent with lower rates of active and passive NaCl transport in the neonatal proximal straight tubule. The effect of luminal sodium and chloride removal on intracellular pH was used to assess the relative rates of Na+/H+and Cl−/base exchange. The rates of Na+/H+and Cl−/base exchange were approximately fivefold less in neonatal proximal straight tubules than adult tubules. In both neonatal and adult proximal straight tubules, the rate of Cl−/base exchange was not affected by formate, bicarbonate, or cyanide and acetazolamide, consistent with Cl−/OH−exchange. These data demonstrate an increase in proximal straight tubule NaCl transport during postnatal renal development.

Evidence for active dipeptide transport in isolated proximal straight tubules

1988 ◽  
Vol 255 (1) ◽  
pp. F177-F181 ◽  
Author(s):  
D. W. Barfuss ◽  
V. Ganapathy ◽  
F. H. Leibach
Keyword(s):  
Basolateral Membrane ◽  
Rabbit Kidney ◽  
Luminal Membrane ◽  
Appearance Rate ◽  
Metabolic Products ◽  
Straight Tubules ◽  
Liquid Chromatographic Analysis ◽  
Dipeptide Transport ◽  
Liquid Chromatographic

Transport of the dipeptide glycylsarcosine (Gly-Sar) was examined in isolated proximal straight tubules of the rabbit kidney by an in vitro microperfusion technique to determine whether it can be actively transported intact. The unidirectional lumen-to-bath flux of Gly-Sar was measured by two separate methods, namely its appearance rate (JA) in the bathing fluid and its disappearance rate (JD) from the luminal fluid. In addition, the cell Gly-Sar concentration was measured immediately after the last flux period. Mean luminal fluid Gly-Sar concentration was 0.22 mM. Transepithelial Gly-Sar flux (260.0 fmol.min-1.mm-1) was greater than could be accounted for by passive leakage, whereas cellular Gly-Sar accumulation (2.72 mM) was greater than could be attributed to passive equilibration across the luminal membrane. High-pressure liquid chromatographic analysis of cellular extract indicated that 63% of the transported Gly-Sar was hydrolyzed within the cell. Analysis of the bath solution revealed that 47% of the radioactivity that crossed the tubule cell was in the form of intact dipeptide, whereas the remainder of the radioactivity was in the form of hydrolytic and metabolic products of Gly-Sar. This indicates that the dipeptide Gly-Sar is actively transported intact at the luminal membrane into the cytosol of proximal straight tubule cells with subsequent hydrolysis. It then exits across the basolateral membrane as intact Gly-Sar and its hydrolytic and metabolic products.

Intracellular potentials in rabbit proximal tubules perfused in vitro

1981 ◽  
Vol 240 (3) ◽  
pp. F200-F210 ◽  
Author(s):  
B. Biagi ◽  
T. Kubota ◽  
M. Sohtell ◽  
G. Giebisch
Keyword(s):  
Membrane Potential ◽  
Basolateral Membrane ◽  
Proximal Tubules ◽  
Rabbit Kidney ◽  
Electrical Measurements ◽  
Proximal Tubular ◽  
The Mean ◽  
Number Of Cells ◽  
Basolateral Membrane Potential

Conventional microelectrodes were used to measure the basolateral membrane potential (VBL) in isolated perfused superficial proximal convoluted (sPCT) and superficial proximal straight (sPST) tubules of the rabbit kidney. Stable recordings for periods up to 2 h can be obtained. The mean +/- SE (n = number of cells) values of VBL were sPCT = -51.0 +/- 1.63 (24) and sPST = -47.0 +/- 0.97 (94) mV. Inhibitors of active transport, ouabain (10(-5) M) and low bath potassium (0.1 mM), caused a significant depolarization of VBL in sPST. In contrast, short-duration bath cooling (10 degrees C) had no significant effect. Removal of luminal glucose caused a larger hyperpolarization in sPCT (-13.9 +/- 1.77 (9) mV) than in sPST (-3.8 +/- 1.02 (5) mV). Removal of luminal glucose and alanine resulted in an even larger hyperpolarization of VBL in sPCT (-19.0 +/- 0.44 (6) mV). Perfusion of the lumen with a solution resembling late proximal tubular fluid in sPST resulted in hyperpolarization of VBL (-4.3 +/- 0.85 (4) mV). Reducing bath pH to 6.7 depolarized VBL (39.9 +/- 1.77 (13) mV). This effect can be associated with a decrease in the relative potassium permeability of the basolateral membrane. These results demonstrate the feasibility of using intracellular electrical measurements to determine both luminal and basolateral membrane characteristics in isolated proximal tubular segments.

Direct measurement of basolateral membrane potentials from cells of the macula densa

1989 ◽  
Vol 257 (3) ◽  
pp. F463-F468 ◽  
Author(s):  
P. D. Bell ◽  
J. Y. Lapointe ◽  
J. Cardinal
Keyword(s):  
Membrane Potential ◽  
Direct Measurement ◽  
Basolateral Membrane ◽  
Membrane Potentials ◽  
Macula Densa ◽  
Rabbit Kidney ◽  
Fluid Composition ◽  
Nacl Solution ◽  
Basolateral Membrane Potential

At the present time, little is known concerning the electrophysiology of the cells of the macula densa and whether or not these cells are electrically responsive to alterations in luminal fluid composition. To investigate this issue, cortical thick ascending limbs (CTAL) containing macula densa and attached glomeruli were dissected from rabbit kidney and the CTAL perfused in vitro. Basolateral membrane potential (Vbl) was measured with microelectrodes in macula densa cells and, for comparison, in cells of the CTAL. Macula densa Vbl averaged -56.5 +/- 7.6 mV (n = 4) at a (n = 22) at 20 mM NaCl, -35.6 +/- 3.9 mV (n = 16) at 45 mM NaCl, and -25.5 +/- 2.6 mV (n = 32) at 150 mm NaCl. Thus macula densa Vbl depolarized markedly (31 mV) when luminal perfusate [NaCl] was increased from low to high values. In contrast, Vbl measured in CTAL cells averaged -62 +/- 6.1 mV (n = 6) in 45 mM NaCl and did not change significantly as perfusate NaCl was increased to 150 mM. In the presence of 150 mM NaCl, luminal application of furosemide (50 microM) produced a small (3.5 +/- 1.1 mV, n = 16) but statistically significant (P less than 0.02) hyperpolarization in macula densa cells, whereas CTAL cell Vbl hyperpolarized markedly (20 +/- 5.7 mV, n = 6) with addition of furosemide. Finally, neither macula densa cells nor the CTAL cells changed Vbl when 45 mM NaCl solution was made hypotonic by removing mannitol.(ABSTRACT TRUNCATED AT 250 WORDS)

Chloride movement across basolateral membrane of Necturus gallbladder epithelium

1984 ◽  
Vol 247 (5) ◽  
pp. C495-C500 ◽  
Author(s):  
R. S. Fisher
Keyword(s):  
Basolateral Membrane ◽  
Membrane Voltage ◽  
Gallbladder Epithelium ◽  
Necturus Gallbladder ◽  
Concentration Changes ◽  
The Difference ◽  
K Concentration ◽  
Low Ionic Strength ◽  
Basolateral Membrane Potential

The relative Cl- and K+ sensitivity of the basolateral membrane potential of the in vitro Necturus gallbladder epithelium was determined. Tissues were punctured with two conventional glass microelectrodes to simultaneously measure the intracellular voltage (Vcs) and the voltage across the subepithelial connective tissue (Vse). Increasing the serosal K+ concentration from 2.5 to 25 mM caused a rapid monotonic depolarization of Vcs without changes of Vse. Reduction of serosal Cl- concentration (98 to 8 mM) caused a transient change of Vse. Thus the difference between Vcs and Vse more accurately reflected the basolateral membrane voltage (Vc) after Cl- concentration changes. The changes of Vc were small and biphasic in response to the decrease of serosal Cl- concentration. Perfusion of a low-ionic-strength solution in the mucosal chamber decreased the current that normally passes through the epithelium. Consistent with the notion that the basolateral voltage changes are attenuated by parallel pathways, the K+-induced depolarization increased by 80% under these conditions. The changes of Vc in response to Cl- substitutions were not different from those of tissue bathed in control solution. Thus the basolateral membrane voltage is relatively insensitive to changes of serosal Cl- concentration. I conclude that Cl- movement across the basolateral membrane is not attributable to simple electrodiffusion, and Cl- exit from these cells at this membrane must be electroneutral.

Interaction of Cl- and other halogens with Cl- transport systems in rabbit cortical collecting duct

1992 ◽  
Vol 263 (5) ◽  
pp. F870-F877 ◽  
Author(s):  
S. Muto ◽  
M. Imai ◽  
Y. Asano
Keyword(s):  
Apical Membrane ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Cell Types ◽  
Transport Systems ◽  
Cortical Collecting Duct ◽  
Cl Transport ◽  
Distinct Cell ◽  
Cl Conductance ◽  
Basolateral Membrane Potential

We have reported that in the rabbit cortical collecting duct (CCD) we can identify electrophysiologically three distinct cell types; the collecting duct (CD) cell and the alpha- and beta-intercalated (IC) cell. To further characterize the Cl- transport properties of each cell type, we examined the interaction between Cl- and other halogens or SCN- in the isolated and perfused CCD by intracellular microelectrode impalement. The rapid depolarization of the basolateral membrane potential (VB) caused by replacement of bath Cl- with each anion revealed that the sequences of apparent halogen selectivity for the basolateral Cl- conductance were similar in all three cell types. The ranking of Cl- > Br- > F- > I- corresponds to the sequence 5 of Eisenman's series, indicating “strong” interaction of the anions with the selectivity site. The basolateral Cl- conductance of these three cell types may share common characteristics, although I- permeability is less in IC cells than in CD cells. Hyperpolarization of the basolateral membrane of the beta-IC cell upon reduction of luminal Cl- reflects alterations in either Cl- entry across the apical membrane, or Cl- exit across the basolateral membrane, or both. Luminal Cl- replacement with each anion showed that the sequence of the hyperpolarization of the basolateral membrane was I- >> cyclamate = SCN- > F- > Br-, suggesting that I-inhibits either apical Cl- entry or basolateral Cl- exit. On the other hand, in the CD cell reduction of the perfusate Cl- by replacement with each anion caused the basolateral membrane to hyperpolarize with a different ranking: cyclamate = F- > I- = SCN- > Br-.(ABSTRACT TRUNCATED AT 250 WORDS)

pH sensitivity of the basolateral membrane of the rabbit proximal tubule

1986 ◽  
Vol 250 (2) ◽  
pp. F261-F266 ◽  
Author(s):  
B. A. Biagi ◽  
M. Sohtell
Keyword(s):  
Potassium Concentration ◽  
Ph Dependence ◽  
Basolateral Membrane ◽  
Rabbit Kidney ◽  
Bathing Solution ◽  
Solution Ph ◽  
Absolute Value ◽  
Ph Dependent ◽  
Basolateral Membrane Potential

Conventional microelectrodes were used to study the effects of bath pH and bicarbonate concentrations on the basolateral membrane potential (Vbl) of cells from the superficial proximal convoluted (PCT) and proximal straight (PST) tubules of the rabbit kidney perfused in vitro. Bathing solution pH was varied over the range of 5.9-7.4 using either control (22-25 mM) or low bicarbonate (5.0-6.6 mM) Ringer solutions and the appropriate CO2 tensions. The results show a strong pH dependence of the steady-state values of Vbl in both the convoluted and straight tubule segments. The pH-dependent depolarization was approximately 35 mV/pH unit change of the bathing solution in the acid direction and could be demonstrated in CO2-free HEPES-buffered solutions. A depolarizing response to increased bath potassium concentration (HK) was observed that was linearly related to the absolute value of the Vbl under control conditions. Under acidotic conditions, reduced HK depolarizations indicate that a decrease in the relative potassium permeability of the basolateral membrane is the principle mechanism underlying the effects of bath pH on Vbl.

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