Conductive properties of papillary surface epithelium

1994 ◽  
Vol 266 (2) ◽  
pp. F259-F265 ◽  
Author(s):  
W. B. Reeves
Keyword(s):  
Cell Membrane ◽  
Apical Membrane ◽  
Ussing Chamber ◽  
Basolateral Membrane ◽  
Transepithelial Resistance ◽  
Surface Epithelium ◽  
Renal Papilla ◽  
Transepithelial Voltage ◽  
K Concentration ◽  
Conductive Properties

The surface epithelium of rabbit renal papilla was dissected free from its supporting tissue and mounted in an Ussing chamber. The conductive properties of the epithelium and of the apical and basolateral cell membranes were examined with KCl-filled microelectrodes. The transepithelial voltage was 0.07 +/- 0.15 mV, and the transepithelial resistance was 107 +/- 15 omega.cm2 (n = 29). The fractional resistance of the apical membrane (fRa) was 0.93 +/- 0.01 (n = 103 cells, 29 tissues). The apical membrane was not conductive to Na+, K+, or Cl-. An increase in the K+ concentration of the basolateral solution from 5 to 50 mM depolarized the basolateral membrane voltage (Vb) from -59 +/- 1.6 to -31.2 +/- 2.2 mV (n = 28 cells) and increased fRa from 0.935 +/- 0.01 to 0.962 +/- 0.01 (P < 0.001, n = 21 cells). Likewise, 5 mM barium in the basolateral solution depolarized Vb from -57.7 +/- 2.0 to -29.8 +/- 2.2 mV (n = 21 cells). A tenfold decrease in the Cl- concentration of the basolateral solution caused an 8.3 +/- 1.9 mV depolarization in Vb. Thus the basolateral cell membrane is conductive to K+ and Cl-. Exposure of the apical membrane to amphotericin B demonstrated that the transepithelial resistance is determined primarily by the paracellular pathway.

cAMP mediates the increase in apical membrane Na+ conductance produced in rat CCD by vasopressin

1990 ◽  
Vol 259 (5) ◽  
pp. F823-F831 ◽  
Author(s):  
J. A. Schafer ◽  
S. L. Troutman
Keyword(s):  
Arginine Vasopressin ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Transepithelial Resistance ◽  
Bathing Solution ◽  
Dibutyryl Camp ◽  
Cyclic Monophosphate ◽  
Collecting Ducts ◽  
Transepithelial Voltage ◽  
Stimulation Of

Experiments were conducted to determine if adenosine 3',5'-cyclic monophosphate (cAMP) mediates the stimulation of Na+ absorption by arginine vasopressin (AVP) in isolated perfused cortical collecting ducts (CCD) from rats treated with deoxycorticosterone pivalate (5 mg im) 5-9 days before study. AVP (220 pM) in the bathing solution hyperpolarized the transepithelial voltage (PDT) from -4.0 +/- 0.8 (SE) to -15.1 +/- 1.4 mV (n = 9, P less than 0.001) and decreased the transepithelial resistance (RT) from 40 +/- 8 to 33 +/- 6 omega.cm2 (n = 5, P less than 0.025). Bath addition of 0.2 mM dibutyryl cAMP (DBcAMP), 0.1 mM isobutylmethylxanthine (IBMX), 0.1 mM DBcAMP plus 0.1 mM IBMX, and 10 or 50 microM forskolin produced the same effects, reversibly hyperpolarizing PDT by 7.0-11.5 mV and decreasing RT by 6-12 omega.cm2. Addition of 10 microM amiloride to the luminal perfusate reduced PDT from -0.9 to +2.0 mV and increased RT in the presence or absence of any of the test agents. Addition of DBcAMP + IBMX or 50 microM forskolin to the bathing solution also reversibly depolarized the basolateral membrane voltage of principal cells by 1-2 mV and decreased the apical membrane fractional resistance from 0.82-0.84 to 0.72-0.77. Both effects were reversed by addition of amiloride to the luminal perfusate. These results demonstrate that cAMP is the intracellular mediator of the increase in apical membrane Na+ conductance produced by AVP in the rat CCD.

Dibutyryl cAMP activates bumetanide-sensitive electrolyte transport in Malpighian tubules

1991 ◽  
Vol 261 (3) ◽  
pp. C521-C529 ◽  
Author(s):  
J. L. Hegarty ◽  
B. Zhang ◽  
T. L. Pannabecker ◽  
D. H. Petzel ◽  
M. D. Baustian ◽  
...  
Keyword(s):  
Yellow Fever ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Fluid Secretion ◽  
Ringer Solution ◽  
Malpighian Tubules ◽  
Membrane Voltage ◽  
Dibutyryl Camp ◽  
K Secretion ◽  
Transepithelial Voltage

The effects of dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) and bumetanide (both 10(-4) M) on transepithelial Na+, K+, Cl-, and fluid secretion and on tubule electrophysiology were studied in isolated Malpighian tubules of the yellow fever mosquito Aedes aegypti. Peritubular DBcAMP significantly increased Na+, Cl-, and fluid secretion but decreased K+ secretion. In DBcAMP-stimulated tubules, bumetanide caused Na+, Cl-, and fluid secretion to return to pre-cAMP control rates and K+ secretion to decrease further. Peritubular bumetanide significantly increased Na+ secretion and decreased K+ secretion so that Cl- and fluid secretion did not change. In bumetanide-treated tubules, the secretagogue effects of DBcAMP are blocked. In isolated Malpighian tubules perfused with symmetrical Ringer solution, DBcAMP significantly hyperpolarized the transepithelial voltage (VT) and depolarized the basolateral membrane voltage (Vbl) with no effect on apical membrane voltage (Va). Total transepithelial resistance (RT) and the fractional resistance of the basolateral membrane (fRbl) significantly decreased. Bumetanide also hyperpolarized VT and depolarized Vbl, however without significantly affecting RT and fRbl. Together these results suggest that, in addition to stimulating electroconductive transport, DBcAMP also activates a nonconductive bumetanide-sensitive transport system in Aedes Malpighian tubules.

Electrophysiological evidence for Cl secretion in shark renal proximal tubules

1985 ◽  
Vol 248 (2) ◽  
pp. F282-F295 ◽  
Author(s):  
K. W. Beyenbach ◽  
E. Fromter
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Proximal Tubules ◽  
In Vitro Perfusion ◽  
Electrophysiological Properties ◽  
Electrophysiological Responses ◽  
Tubule Lumen ◽  
Transepithelial Voltage ◽  
Cl Conductance

The electrophysiology of shark proximal tubules (Squalus acanthias) was investigated using conventional microelectrodes and cable analysis. Under in vitro perfusion with symmetrical Ringer solutions, tubule transepithelial resistance was 36.3 +/- 2.3 omega X cm2 (means +/- SE, n = 44). Other electrophysiological variables varied widely under control conditions. In unstimulated tubules (n = 16) the transepithelial voltage (VT,o) was lumen positive (1.2 +/- 0.2 mV), the basolateral membrane potential (Vbl,x) was -61.3 +/- 1.6 mV, and the fractional resistance of the apical membrane (fRa) was 0.67 +/- 0.02. Spontaneously stimulated tubules (n = 28) had lumen-negative VT,o values (-1.5 +/- 0.4 mV), low Vbl,x values (-41.3 +/- 1.7 mV), and low fRa values (0.30 +/- 0.02). The stimulated state can be induced in unstimulated tubules via treatment with cAMP. Multiple microelectrode impalements in a single tubule revealed epithelial cells sharing similar electrophysiological properties. Selective ion substitutions in the tubule lumen and peritubular bath uncovered an increased Cl conductance in the apical membrane of spontaneously and cAMP-stimulated tubules. Anthracene-9-carboxylic acid tended to reverse the stimulated state, and furosemide hyperpolarized Vbl,x. These results constitute the first evidence for secretory Cl transport in a renal proximal tubule. The electrophysiological responses to ion substitutions, stimulators, and inhibitors are strikingly similar to those of known Cl-transporting epithelia.

Microelectrode assessment of chloride-conductive properties of cortical collecting duct

1984 ◽  
Vol 247 (2) ◽  
pp. F291-F302 ◽  
Author(s):  
S. C. Sansom ◽  
E. J. Weinman ◽  
R. G. O'Neil
Keyword(s):  
Cell Membrane ◽  
Tight Junction ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Apical Cell ◽  
Membrane Conductance ◽  
Cortical Collecting Duct ◽  
Apical Cell Membrane ◽  
Conductive Properties ◽  
Chloride Activity

The chloride-conductive properties of the isolated rabbit cortical collecting duct were assessed with microelectrode techniques. The transepithelial, apical, and basolateral membrane potential differences, Vte, Va, and Vb, respectively, were monitored continuously along with periodic measurements of the transepithelial conductance, Gte, and fractional resistance, fRa (ratio of apical to apical plus basolateral membrane resistance). Active transport was eliminated in all experiments by luminal addition of 50 microM amiloride in HCO3-free solutions. Upon reducing the chloride activity in the bath (gluconate replacement), there was a marked depolarization of Vb and decrease in Gte and fRa, demonstrating a major dependence of the basolateral membrane conductance on the bath chloride activity. However, a significant K+ conductance at that barrier was also apparent since raising the bath K+ concentration caused an increase in Gte and fRa and depolarization of Vb. Lowering the chloride activity of the perfusate caused a consistent decrease of Gte but not of fRa, effects consistent with a high C1- conductance of the tight junction and little, if any, apical membrane C1- conductance. By use of the C1- -dependent conductances, the C1- permeabilities at equilibrium were estimated to be near 1.0 X 10(-5) cm X s-1 for the tight junction, PtiC1, and 5 X 10(-5) cm X s-1 for the basolateral cell membrane, PbC1. It is concluded that the paracellular pathway provides a major route for transepithelial C1- transport. Furthermore, since the isotopically measured C1- permeability is severalfold greater than PtiC1, a significant transcellular flux of C1- must exist, implicating a neutral exchange mechanism at the apical cell membrane in series with the high basolateral membrane C1- conductance.

Conductive properties of the rabbit outer medullary collecting duct: inner stripe

1985 ◽  
Vol 248 (4) ◽  
pp. F500-F506 ◽  
Author(s):  
B. M. Koeppen
Keyword(s):  
Cell Membrane ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Apical Cell ◽  
Rabbit Kidney ◽  
Apical Cell Membrane ◽  
Basolateral Cell Membrane ◽  
Medullary Collecting Duct ◽  
Conductive Properties

Segments of outer medullary collecting duct were dissected from the inner stripe of the rabbit kidney (OMCDi) and perfused in vitro. The conductive properties of the tubule epithelium and individual cell membranes were determined by means of cable analysis and intracellular voltage-recording microelectrodes. In 35 tubules the transepithelial voltage (VT) and resistance (RT) averaged 17.2 +/- 1.4 mV, lumen positive, and 58.6 +/- 5.3 k omega X cm, respectively. The basolateral membrane voltage, (Vbl) was -29.2 +/- 2.1 mV (n = 23). The apical cell membrane did not contain appreciable ion conductances, as evidenced by the high values of apical cell membrane fractional resistance (fRa = Ra/Ra + Rb), which approached unity (0.99 +/- 0.01; n = 23). Moreover, addition of amiloride or BaCl2 to the tubule lumen was without effect on the electrical characteristics of the cell, as was a twofold reduction in luminal [Cl-]. The conductive properties of the basolateral cell membrane were assessed with bath ion substitutions. A twofold reduction in bath [Cl-] depolarized Vbl by 14.7 +/- 0.4 mV (theoretical, 17 mV), while a 10-fold increase in bath [K+] resulted in only a 0.9 +/- 0.4 mV depolarization (theoretical, 61 mV). Substituting bath Na+ with tetramethylammonium (from 150 to 75 mM) was without effect. Reducing bath [HCO-3] from 25 to 5 mM (constant PCO2) resulted in a steady-state depolarization of Vbl of 8.4 +/- 0.4 mV that could not be attributed to conductive HCO-3 movement. Thus, the basolateral cell membrane is predominantly Cl- selective.(ABSTRACT TRUNCATED AT 250 WORDS)

ClC-2 in guinea pig colon: mRNA, immunolabeling, and functional evidence for surface epithelium localization

2002 ◽  
Vol 283 (4) ◽  
pp. G1004-G1013 ◽  
Author(s):  
Marcelo Catalán ◽  
Isabel Cornejo ◽  
Carlos D. Figueroa ◽  
María Isabel Niemeyer ◽  
Francisco V. Sepúlveda ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Guinea Pig ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Distal Colon ◽  
Surface Epithelium ◽  
Patch Clamp Technique ◽  
Chloride Currents ◽  
Kinetics Of

The principal function of the colon in fluid homeostasis is the absorption of NaCl and water. Apical membrane Na+ channels, Na+/H+ and Cl−/HCO[Formula: see text] exchangers, have all been postulated to mediate NaCl entry into colonocytes. The identity of the basolateral exit pathway for Cl− is unknown. We have previously demonstrated the presence of the ClC-2 transcript in the guinea pig intestine. Now we explore in more detail, the tissue and cellular distribution of chloride channel ClC-2 in the distal colon by in situ hybridization and immunohistochemistry. The patch-clamp technique was used to characterize Cl− currents in isolated surface epithelial cells from guinea pig distal colon and these were compared with those mediated by recombinant guinea pig (gp)ClC-2. ClC-2 mRNA and protein were found in the surface epithelium of the distal colon. Immunolocalization revealed that, in addition to some intracellular labeling, ClC-2 was present in the basolateral membranes but absent from the apical pole of colonocytes. Isolated surface epithelial cells exhibited hyperpolarization-activated chloride currents showing a Cl− > I− permeability and Cd2+ sensitivity. These characteristics, as well as some details of the kinetics of activation and deactivation, were very similar to those of recombinant gpClC-2 measured in parallel experiments. The presence of active ClC-2 type currents in surface colonic epithelium, coupled to a basolateral location for ClC-2 in the distal colon, suggests a role for ClC-2 channel in mediating basolateral membrane exit of Cl− as an essential step in a NaCl absorption process.

Electrophysiological characterization of upper portion of descending limb of long-looped nephron

1991 ◽  
Vol 260 (3) ◽  
pp. F311-F316 ◽  
Author(s):  
K. Yoshitomi ◽  
M. Imai
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
High Water ◽  
Membrane Resistance ◽  
Membrane Voltage ◽  
Major Pathway ◽  
K Concentration ◽  
Electrophysiological Characterization

The upper portion of the descending limb of long-looped nephron (LDLu) of the hamster is characterized by high water and ion permeabilities. Although the paracellular route is considered to be the major pathway representing cation permselectivity of this segment, ion transport mechanisms through the transcellular pathway are unknown. To study this issue; we applied cable analysis and conventional microelectrode technique to the hamster LDLu perfused in vitro. The transmural voltage (VT) was not different from zero, and transmural resistance (RT) was very low, 18.3 +/- 2.0 omega.cm2 (n = 12). The basolateral membrane voltage was -80 +/- 2 mV (n = 55), and fractional apical membrane resistance was 0.92 +/- 0.23 (n = 5). Ouabain (0.1 mM) in the bath decreased basolateral membrane voltage (VB) by 23 +/- 3 mV (n = 6, P less than 0.001). Increase in K+ concentration in bath and in lumen from 5 to 50 mM decreased VB by 39 +/- 2 (n = 7, P less than 0.01) and apical membrane voltage (VA) by 10 +/- 1 mV (n = 7, P less than 0.001), respectively. Addition of 2 mM Ba2+ to bath and to lumen decreased VB by -47 +/- 2 (n = 11, P less than 0.001) and decreased VA by 8 +/- 1 mV, respectively. Reduction of HCO3- in bath from 25 to 2.5 mM decreased VB by 4 +/- 1 mV (n = 7, P less than 0.005). Reduction of bath Cl- did not cause any rapid deflection of VB. No appreciable Na+ conductance was detected in the apical membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Nystatin as a probe for investigating the electrical properties of a tight epithelium.

1977 ◽  
Vol 70 (4) ◽  
pp. 427-440 ◽  
Author(s):  
S A Lewis ◽  
D C Eaton ◽  
C Clausen ◽  
J M Diamond
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Conductance ◽  
Voltage Divider ◽  
Junctional Conductance ◽  
Transepithelial Voltage ◽  
Almost All ◽  
Voltage Divider Ratio ◽  
Rabbit Urinary Bladder ◽  
Tight Epithelium

We show how the antibiotic nystatin may be used in conjunction with microelectrodes to resolve transepithelial conductance Gt into its components: Ga, apical membrane conductance; Gbl, basolateral membrane conductance; and Gj, junctional conductance. Mucosal addition of nystatin to rabbit urinary bladder in Na+-containing solutions caused Gt to increase severalfold to ca. 460 micrometerho/muF, and caused the transepithelial voltage Vt to approach +50 mV regardless of its initial value. From measurements of Gt and the voltage-divider ratio as a function of time after addition or removal of nystatin, values for Ga, Gbl, and Gj of untreated bladder could be obtained. Nystatin proved to have no direct effect on Gbl or Gj but to increase Ga by about two orders of magnitude, so that the basolateral membrane then provided almost all of the electrical resistance in the transcellular pathway. The nystatin channel in the apical membrane was more permeable to cations than to anions. The dose-response curve for nystatin had a slope of 4.6. Use of nystatin permitted assessment of whether microelectrode impalement introduced a significant shunt conductance into the untreated apical membrane, with the conclusion that such a shunt was negligible in the present experiments. Nystatin caused a hyperpolarization of the basolateral membrane potential in Na+-containing solutions. This may indicate that the Na+ pump in this membrane is electrogenic.

Unique electrophysiological effects of dinitrophenol in Malpighian tubules

1992 ◽  
Vol 263 (3) ◽  
pp. R609-R614 ◽  
Author(s):  
T. L. Pannabecker ◽  
D. J. Aneshansley ◽  
K. W. Beyenbach
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Resistance ◽  
Malpighian Tubules ◽  
Membrane Voltage ◽  
Shunt Resistance ◽  
Electrophysiological Studies ◽  
Apical Membranes ◽  
Conductive Properties ◽  
Electrophysiological Effects

In the course of electrophysiological studies of Malpighian tubules of the mosquito Aedes aegypti, we have found unusual effects of 2,4-dinitrophenol (DNP) that offer new insights into the electrogenic and conductive properties of the tubule. DNP (10(-4)M) depolarized the basolateral membrane voltage from -58.0 to -3.3 mV, and it depolarized the apical membrane voltage from 110.6 to 8.9 mV. In parallel the transepithelial electrical resistance increased from 11.4 to 16.8 k omega.cm, and the fractional resistance of the apical membrane increased from 0.32 to 0.57. On the assumption that measures of transepithelial resistance in the presence of DNP approach the shunt resistance, the experimental results indicate the following characteristics for the equivalent circuit of the tubule: 1) a shunt resistance that is approximately one-half the transcellular resistance, 2) low and high electromotive forces, respectively, at the basolateral and apical membranes of principal cells, 3) an electrogenic pump at the apical membrane, and 4) a basolateral membrane voltage that is due mostly to the voltage developed by current flow across the basolateral membrane resistance.

ADH increases apical Na+, K+, 2Cl- entry in mouse medullary thick ascending limbs of Henle

1987 ◽  
Vol 252 (1) ◽  
pp. F177-F187 ◽  
Author(s):  
D. A. Molony ◽  
W. B. Reeves ◽  
S. C. Hebert ◽  
T. E. Andreoli
Keyword(s):  
Antidiuretic Hormone ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Resistance ◽  
Mouse Kidney ◽  
Membrane Conductances ◽  
Transepithelial Voltage

These studies were designed to evaluate the mechanism for the ADH-dependent increase in transcellular conductance (Gc, mS X cm-2), which accompanies hormone-dependent increases in the spontaneous transepithelial voltage (Ve, mV) and in the net rate of Cl- absorption in single medullary thick ascending limbs of Henle (mTALH) isolated from mouse kidney. The total transepithelial conductance (Ge, mS X cm-2) was measured with perfusing solutions containing 5 mM K+, zero Ba2+; Gc was that component of Ge blocked by luminal 20 mM Ba2+, zero K+. In paired experiments, antidiuretic hormone (ADH) increased Gc from 44.5 +/- 5.6 to 58.9 +/- 8.9 mS X cm-2 (delta = 14.3 +/- 5.5; P less than 0.02); however, in the presence of 10(-4) M luminal furosemide, ADH had no significant effect on Gc (delta = 5.0 +/- 4.3; NS). A set of similarly paired measurements together with paired observations on the effects of bath Cl- deletion, permitted an assessment of the effect of ADH on the magnitude of the fall in Gc on bath Cl- removal (delta GClc, mS X cm-2). delta GClc was clearly larger with ADH, 29.6 +/- 4.3, than without ADH, 19.2 +/- 1.0 (delta = 10.4 +/- 4.9; P less than 0.05). However, with luminal furosemide, ADH had no significant effect on delta GClc (delta = 1.7 +/- 4.5; NS). These results indicate that the ADH-dependent increase in Gc is secondary to increased salt entry across the apical membrane. We computed apical (ga, mS X cm-2) and basolateral (gb, mS X cm-2) membrane conductances from the Gc measurements and apical-to-basolateral membrane resistance ratios (Ra/Rb) obtained from cell impalement: the ADH-dependent Gc increase was due to an increase in gb, which was blocked entirely by luminal furosemide. We propose that ADH increases the number of functioning apical membrane Na+,K+,2Cl- transport units, and that gb increases because cell Cl- activity rises and depolarizes the basolateral membrane. Thus the calculated cellular Cl- activity was 16.3 mM without ADH, and 25 mM with ADH.

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