Mineralocorticoid regulation of apical cell membrane Na+ and K+ transport of the cortical collecting duct

1985 ◽  
Vol 248 (6) ◽  
pp. F858-F868 ◽  
Author(s):  
S. C. Sansom ◽  
R. G. O'Neil
Keyword(s):  
Cell Membrane ◽  
Tight Junction ◽  
Apical Membrane ◽  
Collecting Duct ◽  
Apical Cell ◽  
Cortical Collecting Duct ◽  
Apical Cell Membrane ◽  
K Secretion ◽  
Junction Conductance ◽  
K Transport

The effects of mineralocorticoid (DOCA) treatment of rabbits on the Na+ and K+ transport properties of the cortical collecting duct apical cell membrane were assessed using microelectrode techniques. Applying standard cable techniques and equivalent circuit analysis to the isolated perfused tubule, the apical cell membrane K+ and Na+ currents and conductances could be estimated from the selective effects of the K+ channel blocker Ba2+ and the Na+ channel blocker amiloride on the apical membrane; amiloride treatment was observed also to decrease the tight junction conductance by an average of 10%. After 1 day of DOCA treatment, the Na+ conductance and current (Na+ influx) of the apical cell membrane doubled and remained elevated with prolonged treatment for up to 2 wk. The apical cell membrane K+ conductance was not influenced after 1 day, although the K+ current (K+ secretion) increased significantly due to an increased driving force for K+ exit. After 4 days or more of DOCA treatment the K+ conductance doubled, resulting in a further modest stimulation in K+ secretion. After 2 wk of DOCA treatment the tight junction conductance decreased by near 30%, resulting in an additional hyperpolarization of the transepithelial voltage, thereby favoring K+ secretion. It is concluded that the acute effect (within 1 day) of mineralocorticoids on Na+ and K+ transport is an increase in the apical membrane Na+ conductance followed by delayed chronic alterations in the apical membrane K+ conductance and tight junction conductance, thereby resulting in a sustained increased capacity of the tubule to reabsorb Na+ and secrete K+.

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.

Characterization of apical cell membrane Na+ and K+ conductances of cortical collecting duct using microelectrode techniques

1984 ◽  
Vol 247 (1) ◽  
pp. F14-F24 ◽  
Author(s):  
R. G. O'Neil ◽  
S. C. Sansom
Keyword(s):  
Cell Membrane ◽  
Collecting Duct ◽  
Apical Cell ◽  
Membrane Voltage ◽  
Cortical Collecting Duct ◽  
Apical Cell Membrane ◽  
Basolateral Cell Membrane ◽  
Luminal Side ◽  
Conductive Properties ◽  
Microelectrode Techniques

The apical cell membrane ionic conductive properties of the isolated perfused rabbit cortical collecting duct (tubule) were assessed at 37 degrees C using microelectrode techniques. In the initial evaluation of the methodology, it was observed that stable cell membrane voltage recordings could be obtained by impaling cells either from the luminal side across the apical cell membrane or from the bath side across the basolateral cell membrane, providing initial evidence supporting the application of these techniques to this tissue. With the latter method of impalement, it was observed that addition of amiloride (50 microM) to the luminal perfusate caused a hyperpolarization of the apical cell membrane voltage, a decrease in the transepithelial conductance, and an increase in the fractional resistance (estimated as the ratio of the resistance of the apical cell membrane to the sum of apical and basolateral cell membrane resistances). These results are consistent with an amiloride-sensitive Na+ conductance at the apical cell border. In a similar manner it was deduced from the effects of elevating K+ in the luminal perfusate from 5 to either 25 or 50 mM that there was a high K+ conductance at the apical border. This conductive pathway was blocked by the luminal addition of 5 mM Ba2+ or reduction of the luminal pH to 4.0. Furthermore, since addition of both amiloride and Ba2+ to the perfusate caused the fractional resistance to increase from 0.52 +/- 0.04 to 0.91 +/- 0.03, the Na+ and K+ conductances are the apparent dominant conductive pathways at that border. It is concluded that microelectrode techniques can be applied successfully to the cortical collecting duct and that the apical cell membrane possesses an amiloride-sensitive Na+ conductance and a Ba2+- and H+-sensitive K+ conductance.

Analysis of K+ transport by rabbit CCD: conductive pathways and K(+)-K+ exchange by Na(+)-K+ pump

1992 ◽  
Vol 262 (1) ◽  
pp. F86-F97 ◽  
Author(s):  
T. Nonaka ◽  
D. H. Warden ◽  
J. B. Stokes
Keyword(s):  
Apical Membrane ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Cortical Collecting Duct ◽  
Na Transport ◽  
Epithelial Na Channels ◽  
Electrophysiological Measurements ◽  
K Secretion ◽  
Cellular Pathways ◽  
K Transport

We studied the cellular pathways of K+ transport by the rabbit cortical collecting duct that was stimulated to absorb Na+ and to secrete K+. The vast majority of K+ secretion (into the lumen) was inhibited by benzamil, a blocker of epithelial Na+ channels. The residual K+ secretion was completely inhibited by ouabain. Thus all active K+ secretion was dependent on Na+ transport by the Na(+)-K+ pump. The passive pathways of K+ transport were further examined using tracer and electrophysiological measurements. K+ transfer across the apical membrane was predominantly or exclusively conductive; the apical K+ conductance was 31 mS/cm2. The basolateral membrane contained two pathways for K+ tracer translocation. The (barium-sensitive) conductive pathway accounted for a relatively small (12-20%) portion of the tracer permeation. A larger pathway appeared to be via K(+)-K+ exchange on the Na(+)-K+ pump. The magnitude of the Ba2(+)-sensitive (basolateral) K+ conductance predicted a substantially larger tracer flux than was actually measured. The best explanation for this difference is the presence of single-file diffusion through K+ channels on the apical and basolateral membranes. An analysis of the electrically silent K+ transport from lumen to bath suggests that the Na(+)-K+ pump can vary the ratio of its Na(+)-K+ and K(+)-K+ modes of operation. When the tubule is actively transporting Na+ and K+, the Na(+)-K+/K(+)-K+ turnover ratio is greater than 7. When Na+ transport is limited by inhibiting Na+ entry across the apical membrane, the ratio falls to less than 1. A major factor determining this ratio is probably the availability of Na+ to the cytoplasmic side of the pump.

Intracellular microelectrode characterization of the rabbit cortical collecting duct

1983 ◽  
Vol 244 (1) ◽  
pp. F35-F47 ◽  
Author(s):  
B. M. Koeppen ◽  
B. A. Biagi ◽  
G. H. Giebisch
Keyword(s):  
Cell Membrane ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Apical Cell ◽  
Fold Increase ◽  
K Channel ◽  
Cortical Collecting Duct ◽  
Apical Cell Membrane ◽  
Basolateral Cell Membrane

Cortical collecting ducts of the rabbit were perfused in vitro and the intracellular potential (Vbl) was measured with KCl-filled microelectrodes. The ratio of apical to basolateral membrane resistance (Ra/Rbl) was estimated from the voltage divider ratio using cable analysis. In control tubules Vbl averaged--84.0 +/- 2.5 mV and Ra/Rbl was 0.83 +/- 0.11. Pretreatment of the rabbits with mineralocorticoid caused Vbl to hyperpolarize to--105.8 +/- 3.1 mV and Ra/Rbl to decrease slightly to 0.62 +/- 0.10. A 10-fold increase of the luminal [K+] caused a 40.6 +/- 3.1 mV depolarization of Vbl in control tubules and a 33.0 +/- 4.2 mV depolarization in tubules from DOCA-pretreated rabbits. Concurrently, Ra/Rbl decreased in both groups, consistent with the existence of a conductive K+ channel at the apical cell membrane. This apical K+ channel was not sensitive to amiloride but was blocked by Ba2+. Conductive movement of Na+ across the apical membrane was also apparent in that Ra/Rbl increased with amiloride from 0.61 +/- 0.10 to 1.45 +/- 0.28. A 10-fold increase in the bath [K+] caused a 28.6 +/- 3.8 and a 49.4 +/- 4.4 mV depolarization of Vbl in tubules obtained from control and DOCA-pretreated rabbits, respectively. In both groups Ra/Rbl increased, suggesting that the basolateral cell membrane also contains a conductive K+ channel. Taken together the results support a model in which the transepithelial reabsorption of Na+ and the transepithelial secretion of K+ are driven by the Na+-K+-ATPase located in the basolateral cell membrane, with passive movement of these ions occurring through separate conductive pathways in the apical cell membrane.

K+ transport in the mesonephric collecting duct system of the toadBufo bufo

2002 ◽  
Vol 205 (7) ◽  
pp. 897-904
Author(s):  
Nadja Møbjerg ◽  
Erik Hviid Larsen ◽  
Ivana Novak
Keyword(s):  
Cell Membrane ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Apical Cell ◽  
K Channel ◽  
Duct System ◽  
Apical Cell Membrane ◽  
Collecting Ducts ◽  
Collecting Tubules ◽  
K Transport

SUMMARYWe studied the mechanisms of K+ transport in cells from isolated and perfused collecting tubules and ducts from the mesonephric kidney of the toad Bufo bufo. Cells were impaled with microelectrodes across the basal cell membrane. The basolateral membrane potential(Vbl) depolarized upon change of bath [K+] from 3 to 20 mmol l-1 demonstrating a large K+ conductance in this membrane. In collecting tubules and collecting ducts a Vbl of -66±2 mV and -74±4 mV depolarized by 30±2 mV and 36±3 mV, respectively (N=23; 15). The K+ channel inhibitor Ba2+ (1 mmol l-1)inhibited the basolateral K+ conductance and depolarized a Vbl of -64±4 mV by 30±6 mV (N=8). Luminal K+ steps (3 to 20 mmol l-1) demonstrated a K+ conductance in the apical cell membrane. In collecting tubules and collecting ducts a Vbl of -70±3 mV and-73±3 mV depolarized by 11±3 mV and 16±3 mV, respectively(N=11; 11). This conductance could also be inhibited by Ba2+, which depolarized a Vbl of -71±5 mV by 9±3 mV (N=5). The pump inhibitor ouabain (1 mmol l-1) depolarized Vbl, but addition of furosemide to bath solution did not affect Vbl. The[K+] in urine varied from 1.3 to 22.8 mmol l-1. In conclusion, we propose that the collecting duct system of B. bufosecretes K+ into the urine via luminal K+channels.

Bovine pancreatic duct cells express cAMP- and Ca(2+)-activated apical membrane Cl- conductances

1997 ◽  
Vol 273 (1) ◽  
pp. G204-G216 ◽  
Author(s):  
L. al-Nakkash ◽  
C. U. Cotton
Keyword(s):  
Epithelial Cells ◽  
Cell Membrane ◽  
Pancreatic Duct ◽  
Apical Membrane ◽  
Apical Cell ◽  
Primary Cultures ◽  
Apical Cell Membrane ◽  
Anion Secretion ◽  
Duct Epithelium ◽  
Cl Permeability

Secretion of salt and water by the epithelial cells that line pancreatic ducts depends on activation of apical membrane Cl- conductance. In the present study, we characterized two types of Cl- conductances present in the apical cell membrane of bovine pancreatic duct epithelial cells. Primary cultures of bovine main pancreatic duct epithelium and an immortalized cell line (BPD1) derived from primary cultures were used. Elevation of intracellular adenosine 3',5'-cyclic monophosphate (cAMP) or Ca2+ in intact monolayers of duct epithelium induced sustained anion secretion. Agonist-induced changes in plasma membrane Cl- permeability were accessed by 36 Cl- efflux, whole cell current recording, and measurements of transepithelial Cl- current across permeabilized epithelial monolayers. Elevation of intracellular cAMP elicited a sustained increase in Cl- permeability, whereas elevation of intracellular Ca2+ induced only a transient increase in Cl- permeability. Ca(2+)- but not cAMP-induced increases in Cl- permeability were abolished by preincubation of cells with the Ca2+ buffer 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, tetra(acetoxymethyl) ester (BAPTA-AM). N-phenylanthranilic acid (DPC; 1 mM) and glibenclamide (100 microM), but not 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS; 500 microM), inhibited the cAMP-induced increase in Cl- permeability. In contrast, DPC and DIDS, but not glibenclamide, inhibited the Ca(2+)-induced increase in Cl- permeability. We conclude from these experiments that bovine pancreatic duct epithelial cells express at least two types of Cl- channels, cAMP and Ca2+ activated, in the apical cell membrane. Because the Ca(2+)-activated increase in Cl- permeability is transient, the extent to which this pathway contributes to sustained anion secretion by the ductal epithelium remains to be determined.

Effect of insulin on potassium secretion in rabbit cortical collecting ducts

1992 ◽  
Vol 262 (1) ◽  
pp. F30-F35 ◽  
Author(s):  
H. Furuya ◽  
K. Tabei ◽  
S. Muto ◽  
Y. Asano
Keyword(s):  
Collecting Duct ◽  
Dependent Manner ◽  
Cortical Collecting Duct ◽  
Plasma Insulin Concentration ◽  
Concentration Dependent Manner ◽  
K Secretion ◽  
Potassium Secretion ◽  
Transepithelial Voltage ◽  
K Transport

Insulin is known to play an important role in the regulation of extrarenal K homeostasis. Previous clearance studies have shown that insulin decreases urinary K excretion, but the responsible nephron segments have not been identified. In this microperfusion study, in vitro, the effect of insulin on K transport in the cortical collecting duct (CCD), which is thought to be an important segment for regulation of the final urinary K excretion, was investigated. Basolateral insulin (10(-6) M) significantly inhibited net K secretion by 20% (mean JK = -26.2 +/- 4.2 peq.mm-1.min-1 for controls compared with -21.1 +/- 3.4 with insulin, P less than 0.001) and depolarized the transepithelial voltage (VT, from -14.6 +/- 3.5 to -10.8 +/- 3.5 mV, P less than 0.005), recovery did not occur over 60 min. Insulin (10(-11)-10(-5) M) depressed K secretion and depolarized the VT in a concentration-dependent manner. The half-maximal concentration was 5 x 10(-10) M, which is within the physiological range of plasma insulin concentration. In tubules of deoxycorticosterone acetate-treated rabbits, insulin also produced a significant fall in K secretion (from -43.4 +/- 7.5 to -36.1 +/- 5.7 peq.mm-1.min-1, P less than 0.05). Although luminal Ba (2 mM) decreased K secretion (from -14.4 +/- 2.9 to -7.0 +/- 1.7 peq.mm-1.min-1), basolateral insulin (10(-6) M) inhibited K secretion further (to -4.7 +/- 1.3 peq.mm-1.min-1, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

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)

K+ and Rb+ transport by the rabbit CCD: Rb+ reduces K+ conductance and Na+ transport

1989 ◽  
Vol 257 (1) ◽  
pp. F43-F52 ◽  
Author(s):  
D. H. Warden ◽  
M. Hayashi ◽  
V. L. Schuster ◽  
J. B. Stokes
Keyword(s):  
Atpase Activity ◽  
Collecting Duct ◽  
Secretory Process ◽  
Cortical Collecting Duct ◽  
K Secretion ◽  
Induced Changes ◽  
The Relationship ◽  
Paracellular Diffusion ◽  
K Permeability ◽  
K Transport

We compared transport of K+ and Rb+ across the rabbit cortical collecting duct to gain insight into the mechanisms of K+ secretion. Passive tracer fluxes, active secretory rates, electrophysiological behavior, and the ability of each ion to support Na+-K+-ATPase activity were determined. When active transport was inhibited by amiloride, K+ permeability was twice the Rb+ permeability. Transepithelial conductance (GT) was half as great in solutions where 5 mM Rb+ replaced 5 mM K+. When 4 mM Ba2+ was added to the lumen, both Rb+ and K+ permeability fell to values not different from that expected for paracellular diffusion. The relationship between Ba2+-induced changes in the K+ and Rb+ permeabilities and in the simultaneously measured GT provides strong evidence that K+ transport across the apical membrane is largely, if not exclusively, conductive. We also determined that net K+ secretion is greater than net Rb+ secretion (when each is the abundant ion). The reasons for this difference probably involve several steps in the K+ secretory process and include the following: 1) reduced ATPase activity in the presence of Rb+ (approximately 80%) compared with K+, 2) reduction of Na+ absorption, and 3) partial blockade of the apical (and perhaps basolateral) K+ conductance. Although there were quantitative differences between K+ and Rb+ transport, we found no evidence suggesting that these ions are transported by different mechanisms.

Sign in / Sign up

Export Citation Format

Share Document