Absence of transepithelial anion exchange by rabbit OMCD: evidence against reversal of cell polarity

1988 ◽  
Vol 255 (2) ◽  
pp. F220-F228 ◽  
Author(s):  
M. Hayashi ◽  
V. L. Schuster ◽  
J. B. Stokes
Keyword(s):  
Anion Exchange ◽  
Cell Polarity ◽  
Rate Coefficient ◽  
Collecting Duct ◽  
Ringer Solution ◽  
Base Line ◽  
Cortical Collecting Duct ◽  
Exchange System ◽  
Outer Medulla ◽  
Medullary Collecting Duct

In the rabbit cortical collecting duct (CCD), Cl tracer crosses the epithelium predominantly via an anion exchange system that operates in either a Cl-Cl or Cl-HCO3 exchange mode. In the present study, we used the 36Cl lumen-to-bath rate coefficient (KCl, nm/s), a sensitive measurement of CCD transepithelial anion transport, to investigate the nature of Cl transport in the medullary collecting duct dissected from inner stripe, outer medulla (OMCD). The KCl in OMCD perfused and bathed in HCO3-Ringer solution was low (46.2 +/- 8.5 nm/s) and similar to that value observed in the CCD when anion exchange is inhibited and Cl permeates the epithelium by diffusion. Unlike KCl in CCD, KCl in OMCD was not stimulated by adenosine 3',5'-cyclic monophosphate (cAMP). OMCD KCl was not altered by bath Cl and/or HCO3 removal, demonstrating the absence of transepithelial Cl-Cl and Cl-HCO3 exchange. To test the hypothesis that metabolic alkalosis could reverse the polarity of intercalated cells and thus induce an apical Cl-HCO3 exchanger in H+-secreting OMCD cells, we measured KCl in OMCD from rabbits made alkalotic by deoxycorticosterone and furosemide. Although the base-line KCl was slightly higher than in OMCD from control rabbits, the value was still far lower than the KCl under comparable conditions in CCD. Moreover, KCl in OMCD from alkalotic rabbits was unchanged by cAMP, or by sequential removal of bath HCO3 and Cl. Immunocytochemistry using peanut lectin and a monoclonal antibody to-erythrocyte band 3 failed to reveal any evidence for alkalosis-induced reversal of either CCD or OMCD intercalated cell polarity.(ABSTRACT TRUNCATED AT 250 WORDS)

Stimulation of Cl- self exchange by intracellular HCO3- in rabbit cortical collecting duct

1989 ◽  
Vol 257 (1) ◽  
pp. C94-C101 ◽  
Author(s):  
K. Matsuzaki ◽  
J. B. Stokes ◽  
V. L. Schuster
Keyword(s):  
Anion Exchange ◽  
Intracellular Ph ◽  
Rate Coefficient ◽  
Collecting Duct ◽  
Cortical Collecting Duct ◽  
High K ◽  
Shift Experiment ◽  
Ethanesulfonic Acid ◽  
The Individual ◽  
Stimulation Of

In rabbit cortical collecting duct, Cl- self exchange accounts for most of the transepithelial Cl- tracer rate coefficient, KCl (nm/s); a small fraction is effected by Cl--HCO3- exchange and Cl- diffusion. We previously reported that changing from a CO2-free N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) bath to a 5% CO2-25 mM HCO3- bath stimulates Cl- self exchange. Here, we examine in further detail the individual components of the CO2-HCO3- system that stimulate KCl. Addition of 0.5% CO2 to a HEPES bath (final pH = 7.24) stimulated KCl by 70 +/- 19 nm/s, a delta KCl comparable to that induced by 1% CO2 (pH 7.12), 6% CO2 (pH 6.6), or 6% CO2-25 mM HCO3- (pH 7.4). The roles of intracellular pH (pHi) and HCO3- concentration were examined by clamping pHi using high K+ and nigericin. Increasing pHi from 6.9 to 7.6 in solutions without exogenous CO2 or HCO3- increased KCl by 71 +/- 17 nm/s. These results suggest that pHi might regulate anion exchange. However, during such a pHi-shift experiment, metabolically derived CO2 produces a concomitant change in intracellular HCO3- concentration [( HCO3-]i). To determine whether an increase in [HCO3-]i could stimulate Cl- self exchange, we replaced HEPES with 6% CO2-5 mM HCO3- isohydrically (pHi clamped at 6.9). With this increase in [HCO3-]i at constant pHi, KCl increased by 51 +/- 10 nm/s. These maneuvers had negligible effects on Cl- diffusion and Cl--HCO3- exchange. These experiments demonstrate that increases in cell [HCO3-] (or perhaps CO2) can stimulate transepithelial anion exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretion of salt and water into the medullary collecting duct of Ringer-infused rats

1975 ◽  
Vol 228 (2) ◽  
pp. 565-568 ◽  
Author(s):  
H Sonnenberg
Keyword(s):  
Collecting Duct ◽  
Extracellular Fluid ◽  
Ringer Solution ◽  
Tubular Secretion ◽  
Fluid Loading ◽  
Outer Medulla ◽  
Nephron Segments ◽  
Medullary Collecting Duct ◽  
Filtered Load ◽  
Sodium And Potassium

Using a microcatheterization technique, the contribution of the collecting duct to the renal response to extracellular fluid volume expansion was studied in anesthetized rats. During intravenous infusion of Ringer solution (0.25 ml/min per 100 g body wt), urinary excretion of fluid, sodium, and potassium was 365 mul/min per g kidney wt (V), 52.6 mueq/min per g kidney wt (UNaV), and 3.86 mueq/min per g kidney wt (UKV), representing 23, 24, and 65% of filtered load, respectively. Analysis of collecting duct fluid from cortex and outer medulla indicated continued net reabsorption of ions and water in these nephron segments; in contrast, in inner medulla net secretion of Na, K, and fluid into the collecting duct was demonstrated. Addition of sodium and water was equivalent to approximately 10% of filtered load. It is concluded that under the stress of extreme intravenous fluid loading tubular secretion of salt and water into the inner medullary collecting duct contributes importantly to diuresis and natriuresis. The mechanism of such secretion remains undetermined.

Distribution of kallikrein-binding protein mRNA in kidneys and difference between SHR and WKY rats

1994 ◽  
Vol 267 (2) ◽  
pp. F325-F330 ◽  
Author(s):  
T. Yang ◽  
Y. Terada ◽  
H. Nonoguchi ◽  
M. Tsujino ◽  
K. Tomita ◽  
...  
Keyword(s):  
Blot Analysis ◽  
Binding Protein ◽  
Collecting Duct ◽  
Cortical Collecting Duct ◽  
Sprague Dawley ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Sd Rats ◽  
Medullary Collecting Duct ◽  
Wistar Kyoto

We investigated kallikrein-binding protein (KBP) mRNA distribution in the kidney of Sprague-Dawley (SD) rats, spontaneously hypertensive rats (SHR), and Wistar-Kyoto strain (WKY) rats. Northern blot analysis revealed that KBP mRNA was located mainly in the medulla and with lower amounts in SHR than in WKY rats. KBP mRNA in microdissected nephron segments was detected by reverse transcription and polymerase chain reaction (RT-PCR) followed by Southern blot analysis. In SD rats, the most abundant signals were consistently found in inner medullary collecting duct (IMCD), with small amounts in outer medullary collecting duct, proximal convoluted tubule, and glomerulus. No signals were found in connecting tubule and cortical collecting duct. The nephron distribution of KBP mRNA was similar in WKY and SD rats. Only a small amount of signal was found, however, in IMCD of SHR. In conclusion, 1) KBP mRNA was predominantly distributed in the medullary segments of the distal nephron, downstream from the known kallikrein activity site in the collecting duct, and 2) KBP mRNA expression was significantly decreased in the kidney of SHR.

Regional and segmental localization of AE2 anion exchanger mRNA and protein in rat kidney

1995 ◽  
Vol 269 (4) ◽  
pp. F461-F468 ◽  
Author(s):  
F. C. Brosius ◽  
K. Nguyen ◽  
A. K. Stuart-Tilley ◽  
C. Haller ◽  
J. P. Briggs ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Chloride Concentration ◽  
Transepithelial Transport ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Base Exchange ◽  
Medullary Thick Ascending Limb ◽  
Nephron Segment ◽  
Medullary Collecting Duct

Chloride/base exchange activity has been detected in every mammalian nephron segment in which it has been sought. However, in contrast to the Cl-/HCO3- exchanger AE1 in type A intercalated cells, localization of AE2 within the kidney has not been reported. We therefore studied AE2 expression in rat kidney. AE2 mRNA was present in cortex, outer medulla, and inner medulla. Semiquantitative polymerase chain reaction of cDNA from microdissected tubules revealed AE2 cDNA levels as follows [copies of cDNA derived per mm tubule (+/- SE)]: proximal convoluted tubule, 688 +/- 161; proximal straight tubule, 652 +/- 189; medullary thick ascending limb, 1,378 +/- 226; cortical thick ascending limb, 741 +/- 24; cortical collecting duct, 909 +/- 71; and outer medullary collecting duct, 579 +/- 132. AE2 cDNA was also amplified in thin limbs and in inner medullary collecting duct. AE2 polypeptide was detected in all kidney regions. AE2 mRNA and protein were also detected in several renal cell lines. The data are compatible with the postulated roles of AE2 in maintenance of intracellular pH and chloride concentration and with its possible participation in transepithelial transport.

Axial heterogeneity of rabbit cortical collecting duct

1991 ◽  
Vol 260 (4) ◽  
pp. F498-F505
Author(s):  
C. L. Emmons ◽  
K. Matsuzaki ◽  
J. B. Stokes ◽  
V. L. Schuster
Keyword(s):  
Cross Sections ◽  
Cell Function ◽  
Rate Coefficient ◽  
Collecting Duct ◽  
Lectin Binding ◽  
Cell Types ◽  
Intercalated Cells ◽  
Cortical Collecting Duct ◽  
Principal Cells ◽  
Inner Cortex

The rabbit cortical collecting duct (CCD) consists of three major cell types: principal cells transport K+, beta-intercalated cells absorb Cl-, and alpha-intercalated cells secrete H+. We used functional and histological methods to assess axial distribution of these cell types along rabbit CCD. In perfused CCDs, lumen-to-bath Rb+ rate coefficient (an index of principal cell K+ transport) was not different in tubules from outer cortex (1 mm from renal surface) compared with those from inner cortex (2 mm from renal surface), suggesting that principal cell function is homogeneous along the CCD. In contrast, Cl- rate coefficient (a measure of beta-intercalated cell function) was twice as high in CCDs from outer compared with inner cortex, suggesting heterogeneity of beta-intercalated cells along the CCD. To further investigate these regional differences, we fixed and embedded kidneys and identified three cell types in CCD cross sections using carbonic anhydrase staining and peanut lectin binding. Comparing tubule cross sections from outer with those from inner cortex, we found no axial difference in the fraction of cells that were either principal cells (64%) or total (lectin binding and nonlectin binding) intercalated cells (36%). However, the lectin-binding intercalated cell subset was significantly increased in outer compared with inner cortex. We conclude that there is not heterogeneity of principal cells along the rabbit CCD; however, beta-cell number and function are increased in outer CCD. Collecting duct heterogeneity begins within the cortical segment.

In vitro perfusion of chinchilla thin limb segments: urea and NaCl permeabilities

1993 ◽  
Vol 264 (2) ◽  
pp. F337-F343 ◽  
Author(s):  
C. L. Chou ◽  
M. A. Knepper
Keyword(s):  
Collecting Duct ◽  
Middle Part ◽  
Urinary Concentration ◽  
Transport Pathway ◽  
Outer Medulla ◽  
Medullary Collecting Duct ◽  
Rapid Transport ◽  
Dilution Potential ◽  
Passive Model

We measured the urea and NaCl permeabilities (Purea and PNaCl, respectively) of the following nephron segments from chinchilla: the upper part of the long-loop descending limb (from outer medulla, LDLu), the middle part of the long-loop descending limb (from outer 30% of the inner medulla, LDLm), the lower part of the long-loop descending limb (from deep inner medulla, LDLl), and the thin ascending limb (from deep inner medulla, ATL). We found that Purea (x10(-5) cm/s) was relatively low in the LDLu (3.3), but that the value was larger in the inner medullary thin descending limb (16.8 for LDLm and 47.6 for LDLl). The ATL had an even higher value (170). Phloretin, 0.25 mM, added to the peritubular bath had no effect on Purea of these segments, suggesting that the rapid transport rate is not due to a phloretin-sensitive facilitated transport pathway like that seen in the inner medullary collecting duct. PNaCl (x10(-5) cm/s) also increased with distance along the length of the thin descending limb (LDLu, 11.7; LDLm, 41.2; LDLl, 98.4; and ATL, 321). Calculations from NaCl dilution potential measurements showed that LDLu was Na+ permselective, whereas LDLl and ATL were Cl- permselective. High solute permeabilities in the inner medullary thin descending limb contradict a major requirement of the passive model of urinary concentration developed previously (J. P. Kokko and F. C. Rector, Jr. Kidney Int. 2: 214-223, 1972; and J. L. Stephenson. Kidney Int. 2: 85-94, 1972).

Renal expression of the ammonia transporters, Rhbg and Rhcg, in response to chronic metabolic acidosis

2006 ◽  
Vol 290 (2) ◽  
pp. F397-F408 ◽  
Author(s):  
Ramanathan M. Seshadri ◽  
Janet D. Klein ◽  
Shelley Kozlowski ◽  
Jeff M. Sands ◽  
Young-Hee Kim ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Protein Expression ◽  
Mrna Expression ◽  
Collecting Duct ◽  
Broad Band ◽  
Ammonia Excretion ◽  
Intercalated Cells ◽  
Outer Medulla ◽  
Chronic Metabolic Acidosis ◽  
Medullary Collecting Duct

Chronic metabolic acidosis induces dramatic increases in net acid excretion that are predominantly due to increases in urinary ammonia excretion. The current study examines whether this increase is associated with changes in the expression of the renal ammonia transporter family members, Rh B glycoprotein (Rhbg) and Rh C glycoprotein (Rhcg). Chronic metabolic acidosis was induced in Sprague-Dawley rats by HCl ingestion for 1 wk; control animals were pair-fed. After 1 wk, metabolic acidosis had developed, and urinary ammonia excretion increased significantly. Rhcg protein expression was increased in both the outer medulla and the base of the inner medulla. Intercalated cells in the outer medullary collecting duct (OMCD) and in the inner medullary collecting duct (IMCD) in acid-loaded animals protruded into the tubule lumen and had a sharp, discrete band of apical Rhcg immunoreactivity, compared with a flatter cell profile and a broad band of apical immunolabel in control kidneys. In addition, basolateral Rhcg immunoreactivity was observed in both control and acidotic kidneys. Cortical Rhcg protein expression and immunoreactivity were not detectably altered. Rhcg mRNA expression was not significantly altered in the cortex, outer medulla, or inner medulla by chronic metabolic acidosis. Rhbg protein and mRNA expression were unchanged in the cortex, outer and inner medulla, and no changes in Rhbg immunolabel were evident in these regions. We conclude that chronic metabolic acidosis increases Rhcg protein expression in intercalated cells in the OMCD and in the IMCD, where it is likely to mediate an important role in the increased urinary ammonia excretion.

Immunolocalization of electroneutral Na-HCO3 − cotransporter in rat kidney

2000 ◽  
Vol 279 (5) ◽  
pp. F901-F909 ◽  
Author(s):  
Henrik Vorum ◽  
Tae-Hwan Kwon ◽  
Christiaan Fulton ◽  
Brian Simonsen ◽  
Inyeong Choi ◽  
...  
Keyword(s):  
Plasma Membranes ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Electron Microscopic Level ◽  
Thick Ascending Limb ◽  
Intercalated Cells ◽  
Electron Microscopic ◽  
Outer Medulla ◽  
Outer Stripe ◽  
Medullary Collecting Duct

An electroneutral Na-HCO3 − cotransporter (NBCN1) was recently cloned, and Northern blot analyses indicated its expression in rat kidney. In this study, we determined the cellular and subcellular localization of NBCN1 in the rat kidney at the light and electron microscopic level. A peptide-derived antibody was raised against the COOH-terminal amino acids of NBCN1. The affinity-purified antibody specifically recognized one band, ∼180 kDa, in rat kidney membranes. Peptide- N-glycosidase F deglycosylation reduced the band to ∼140 kDa. Immunoblotting of membrane fractions from different kidney regions demonstrated strong signals in the inner stripe of the outer medulla (ISOM), weaker signals in the outer stripe of the outer medulla and inner medulla, and no labeling in cortex. Immunocytochemistry demonstrated that NBCN1 immunolabeling was exclusively observed in the basolateral domains of thick ascending limb (TAL) cells in the outer medulla (strongest in ISOM) but not in the cortex. In addition, collecting duct intercalated cells in the ISOM and in the inner medulla also exhibited NBCN1 immunolabeling. Immunoelectron microscopy demonstrated that NBCN1 labeling was confined to the basolateral plasma membranes of TAL and collecting duct type A intercalated cells. Immunolabeling controls were negative. By using 2,7-bis-carboxyethyl-5,6-caboxyfluorescein, intracellular pH transients were measured in kidney slices from ISOM and from mid-inner medulla. The results revealed DIDS-sensitive, Na- and HCO3 −-dependent net acid extrusion only in the ISOM but not in mid-inner medulla, which is consistent with the immunolocalization of NBCN1. The localization of NBCN1 in medullary TAL cells and medullary collecting duct intercalated cells suggests that NBCN1 may be important for electroneutral basolateral HCO3 − transport in these cells.

H(+)-K(+)-ATPase activity in rat collecting duct segments

1992 ◽  
Vol 262 (4) ◽  
pp. F692-F695 ◽  
Author(s):  
J. D. Gifford ◽  
L. Rome ◽  
J. H. Galla
Keyword(s):  
Atpase Activity ◽  
Marked Decrease ◽  
Collecting Duct ◽  
Intercalated Cells ◽  
Cortical Collecting Duct ◽  
Acid Base ◽  
Medullary Collecting Duct ◽  
Gastric Proton Pump

Previous studies have suggested the presence of an H(+)-K(+)-ATPase in rat cortical and medullary intercalated cells with similar properties to the gastric proton pump. The purpose of this study was to determine the functional contribution of an H(+)-K(+)-adenosinetriphosphatase(ATPase) to total CO2 (tCO2) transport along the rat collecting duct. After baseline determination of tCO2 transport in isolated perfused collecting duct segments, Sch 28080 (10 microM) was added to either the perfusate or bath. When Sch 28080 was added to the perfusate, there was no effect in the cortical collecting duct (CCD, 20.8 +/- 6.7 vs. 25.3 + 3.0 pmol.mm-1.min-1), but a marked decrease in tCO2 absorption was effected in both the outer medullary (OMCD, 37.6 + 6.2 vs. 10.7 +/- 4.1 pmol.mm-1.min-1) and initial inner medullary collecting duct (IMCD1, 34.4 +/- 8.1 vs. 16.2 +/- 5.6 pmol.mm-1.min-1). In the CCD from rats with acute alkalosis in vivo, Sch 28080 added to the bath inhibited tCO2 secretion in the CCD (-17.1 +/- 4.4 vs 3.5 + 3.3 pmol.mm-1.min-1). These findings suggest that 1) H(+)-K(+)-ATPase is important in tCO2 absorption in the OMCD and IMCD1 and in tCO2 secretion in the CCD, 2) HCO3(-)-absorbing intercalated cells differ functionally in the cortex and medulla, 3) HCO3- secretion is not the reverse process of HCO3- absorption in the CCD, and 4) H(+)-K(+)-ATPase is important in distal acidification under normal and altered acid-base conditions.

Apical proton secretion by the inner stripe of the outer medullary collecting duct

1999 ◽  
Vol 276 (4) ◽  
pp. F606-F613 ◽  
Author(s):  
I. David Weiner ◽  
Amy E. Frank ◽  
Charles S. Wingo ◽  
Keyword(s):  
Collecting Duct ◽  
Principal Cell ◽  
Cortical Collecting Duct ◽  
Proton Secretion ◽  
Intercalated Cell ◽  
Acid Load ◽  
Medullary Collecting Duct ◽  
The One ◽  
Proton Transporters

The inner stripe of outer medullary collecting duct (OMCDis) is unique among collecting duct segments because both intercalated cells and principal cells secrete protons and reabsorb luminal bicarbonate. The current study characterized the mechanisms of OMCDis proton secretion. We used in vitro microperfusion, and we separately studied the principal cell and intercalated cell using differential uptake of the fluorescent, pH-sensitive dye, 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Both the principal cell and intercalated cell secreted protons, as identified as Na+/H+exchange-independent intracellular pH (pHi) recovery from an intracellular acid load. Two proton transport activities were identified in the principal cell; one was luminal potassium dependent and Sch-28080 sensitive and the other was luminal potassium independent and luminal bafilomycin A1sensitive. Thus the OMCDisprincipal cell expresses both apical H+-K+-ATPase and H+-ATPase activity. Intercalated cell Na+/H+exchange-independent pHi recovery was approximately twice that of the principal cell and was mediated by pharmacologically similar mechanisms. We conclude 1) the OMCDis principal cell may contribute to both luminal potassium reabsorption and urinary acidification, roles fundamentally different from those of the principal cell in the cortical collecting duct; and 2) the OMCDis intercalated cell proton transporters are functionally similar to those in the principal cell, raising the possibility that an H+-K+-ATPase similar to the one present in the principal cell may contribute to intercalated cell proton secretion.

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