Expression of TWIK-1, a novel weakly inward rectifying potassium channel in rat kidney

1998 ◽  
Vol 275 (6) ◽  
pp. C1602-C1609 ◽  
Author(s):  
F. Cluzeaud ◽  
R. Reyes ◽  
B. Escoubet ◽  
M. Fay ◽  
M. Lazdunski ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Cell Types ◽  
Loop Of Henle ◽  
Membrane Domains ◽  
Cortical Collecting Duct ◽  
Double Immunofluorescence ◽  
Distinct Cell ◽  
Weakly Inward ◽  
Low K

Several K+ conductances have been identified in the kidney, with specific properties and localization in distinct cell types and membrane domains. On the other hand, several K+ channels have been characterized at the molecular level. By immunolocalization, we show that a new inward rectifying K+channel, TWIK-1, is specifically expressed in distinct tubular segments and cell types of the rat kidney. In the proximal tubule, TWIK-1 prevails in the initial portions (convoluted part), where it is restricted to the apical (brush-border) membrane. In the collecting duct, immunofluorescence was intracellular or confined to the apical membrane and restricted to intercalated cells, i.e., in cells lacking aquaporin-2, as shown by double immunofluorescence. TWIK was also expressed in medullary and cortical parts of the thick limb of the loop of Henle, identified with an anti-Tamm-Horsfall protein antibody (double immunofluorescence). The intensity of TWIK-1 immunolabeling was unchanged in rats fed a low-Na+ or a low-K+ diet. Because TWIK-1 shares common properties with the low-conductance apical K+ channel of the collecting duct, we propose that it could play a role in K+ secretion, complementary to ROMK, another recently characterized K+ channel located in principal cells of the cortical collecting duct and in the loop of Henle.

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)

Differentiation of intercalated cells in developing rat kidney: an immunohistochemical study

1994 ◽  
Vol 266 (6) ◽  
pp. F977-F990 ◽  
Author(s):  
J. Kim ◽  
C. C. Tisher ◽  
K. M. Madsen
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Type A ◽  
Cell Types ◽  
Renal Development ◽  
Intercalated Cells ◽  
Type B ◽  
Fetal Kidney ◽  
Distinct Cell ◽  
Developing Rat

Intercalated cells are present in both the collecting duct, which is derived from the ureteric bud, and the connecting tubule (CNT), which is part of the nephron and thus is developed from the metanephric blastema. However, the embryologic origin of the intercalated cells has not been established. Two populations of intercalated cells, type A and type B, exist in the CNT and the cortical collecting duct (CCD). It is uncertain, however, whether these cells represent truly distinct cell types or whether one is derived from the other. In this study we have used specific antibodies to carbonic anhydrase II (CA II), H(+)-adenosinetriphosphatase (H(+)-ATPase), and band 3 protein to identify subpopulations of intercalated cells, to determine the site and time of their appearance, and to follow their differentiation in the developing rat kidney. Prenatal kidneys from 16-, 17-, 18-, and 20-day-old fetuses, and postnatal kidneys from 0-, 3-, 7-, 14-, and 21-day-old pups were preserved for immunohistochemical studies. Immunostaining for CA II and H(+)-ATPase appeared simultaneously in a subpopulation of cells in the CNT and the medullary collecting duct (MCD) of the 18-day-old fetus, suggesting that intercalated cells differentiate from separate foci, one in the nephron and one in the collecting duct. Cells with apical and cells with basolateral labeling for H(+)-ATPase appeared in the CNT and MCD at 18 days of gestation, indicating that type A and type B cells differentiate simultaneously during renal development. Band 3 immunostaining was very weak in the fetal kidney, but a striking increase in labeling was observed in the 3-day-old kidney, suggesting that there is an activation of acid-secreting cells shortly after birth. In the fetal kidney, immunostaining for CA II and H(+)-ATPase was observed in cells throughout the MCD and on the papillary surface. After birth, immunostaining gradually disappeared from both the papillary surface and the terminal inner MCD, and cells with basolateral labeling for H(+)-ATPase gradually disappeared from the outer MCD. The results of this study suggest that type A and type B intercalated cells represent distinct cell types that derive from undifferentiated cells at two separate foci, one in the nephron and one in the collecting duct. Our results also suggest that entire populations of intercalated cells are eliminated from the collecting duct during normal renal development.

scholarly journals Dietary K regulates ROMK channels in connecting tubule and cortical collecting duct of rat kidney

2009 ◽  
Vol 296 (2) ◽  
pp. F347-F354 ◽  
Author(s):  
Gustavo Frindt ◽  
Anish Shah ◽  
Johan Edvinsson ◽  
Lawrence G. Palmer
Keyword(s):  
Collecting Duct ◽  
Rat Kidney ◽  
Outward Current ◽  
Equilibrium Potential ◽  
Cortical Collecting Duct ◽  
Pipette Solution ◽  
Connecting Tubule ◽  
Outward Currents ◽  
High K ◽  
Low K

The activity of ROMK channels in rat kidney tubule cells was assessed as tertiapin-Q (TPNQ)-sensitive current under whole cell clamp conditions. With an external K+ concentration of 5 mM and an internal K+ concentration of 140 mM and the membrane potential clamped to 0 mV, TPNQ blocked outward currents in principal cells of the cortical collecting duct (CCD) outer medullary collecting duct and connecting tubule (CNT). The apparent Ki was 5.0 nM, consistent with its interaction with ROMK. The TPNQ-sensitive current reversed at voltages close to the equilibrium potential for K+. The currents were reduced when the pipette solution contained ATP. In the CCD, the average TPNQ-sensitive outward current ( ISK) was 476 ± 48 pA/cell in control animals on a 1% KCl diet. ISK increased to 1,255 ± 140 pA when animals were maintained on a high-K (10% KCl) diet for 7 days and decreased to 314 ± 46 pA after 7 days on a low-K (0.1% KCl) diet. In the CNT, ISK was 360 ± 30 pA on control, 1,160 ± 110 on high-K, and 166 ± 16 pA on low-K diets. The results indicate that ROMK channel activity is highly regulated by dietary K in both the CCD and the CNT.

scholarly journals Localization of Inward Rectifier Potassium Channel Kir7.1 in the Basolateral Membrane of Distal Nephron and Collecting Duct

2000 ◽  
Vol 11 (11) ◽  
pp. 1987-1994
Author(s):  
KAYOKO OOKATA ◽  
AKIHIRO TOJO ◽  
YOSHIRO SUZUKI ◽  
NOBUHIRO NAKAMURA ◽  
KENJIRO KIMURA ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Inward Rectifier ◽  
Kidney Cortex ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
Connecting Tubule ◽  
Low K

Abstract. Inward rectifier potassium channels (Kir) play an important role in the K+ secretion from the kidney. Recently, a new subfamily of Kir, Kir7.1, has been cloned and shown to be present in the kidney as well as in the brain, choroid plexus, thyroid, and intestine. Its cellular and subcellular localization was examined along the renal tubule. Western blot from the kidney cortex showed a single band for Kir7.1 at 52 kD, which was also observed in microdissected segments from the thick ascending limb of Henle, distal convoluted tubule (DCT), connecting tubule, and cortical and medullary collecting ducts. Kir7.1 immunoreactivity was detected predominantly in the DCT, connecting tubule, and cortical collecting duct, with lesser expression in the thick ascending limb of Henle and in the medullary collecting duct. Kir7.1 was detected by electron microscopic immunocytochemistry on the basolateral membrane of the DCT and the principal cells of cortical collecting duct, but neither type A nor type B intercalated cells were stained. The message levels and immunoreactivity were decreased under low-K diet and reversed by low-K diet supplemented with 4% KCl. By the double-labeling immunogold method, both Kir7.1 and Na+, K+-ATPase were independently located on the basolateral membrane. In conclusion, the novel Kir7.1 potassium channel is located predominantly in the basolateral membrane of the distal nephron and collecting duct where it could function together with Na+, K+-ATPase and contribute to cell ion homeostasis and tubular K+ secretion.

Regulation of AE2 mRNA expression in the cortical collecting duct by acid/base balance

1998 ◽  
Vol 274 (3) ◽  
pp. F596-F601 ◽  
Author(s):  
Géza Fejes-Tóth ◽  
Erzsébet Rusvai ◽  
Emily S. Cleaveland ◽  
Anikó Náray-Fejes-Tóth
Keyword(s):  
Mrna Expression ◽  
Collecting Duct ◽  
Cell Types ◽  
Alkaline Media ◽  
Mrna Levels ◽  
Intercalated Cells ◽  
Cortical Collecting Duct ◽  
Acid Base Balance ◽  
Acid Base ◽  
Base Balance

AE2 mRNA and protein is expressed in several nephron segments, one of which is the cortical collecting duct (CCD). However, the distribution of AE2 among the different cell types of the CCD and the function of AE2 in the kidney are not known. The purpose of this study was to determine the distribution of AE2 mRNA among the three CCD cell types and to examine the effects of changes in acid/base balance on its expression. Following NH4Cl (acid) or NaHCO3 (base) loading of rabbits for ∼18 h, CCD cells were isolated by immunodissection. AE2 mRNA levels were determined by RT-PCR and were normalized for β-actin levels. We found that CCD cells express high levels of AE2 mRNA (∼500 copies/cell). AE2 mRNA levels were significantly higher in CCD cells originating from base-loaded than acid-loaded rabbits, with an average increase of 3.7 ± 1.07-fold. The effect of pH on AE2 mRNA levels was also tested directly using primary cultures of CCD cells. CCD cells incubated in acidic media expressed significantly lower levels of AE2 mRNA than those in normal or alkaline media. Experiments with isolated principal cells, α-intercalated cells, and β-intercalated cells (separated by fluorescence-activated cell sorting) demonstrated that AE2 mRNA levels are comparable in the three collecting duct cell subtypes and are similarly regulated by changes in acid/base balance. Based on these results, we conclude that adaptation to changes in extracellular H+ concentration is accompanied by opposite changes in AE2 mRNA expression. The observations that AE2 mRNA is not expressed in a cell-type-specific manner and that changes in acid/base balance have similar effects on each CCD cell subtype suggest that AE2 might serve a housekeeping function rather than being the apical anion exchanger of β-intercalated cells.

Oxytocin affects apical sodium conductance in rabbit cortical collecting duct

1993 ◽  
Vol 265 (4) ◽  
pp. F487-F503 ◽  
Author(s):  
T. Inoue ◽  
M. Naruse ◽  
M. Nakayama ◽  
K. Kurokawa ◽  
T. Sato
Keyword(s):  
Receptor Antagonist ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Physiological Role ◽  
Free Calcium ◽  
Second Phase ◽  
Dependent Manner ◽  
Cortical Collecting Duct ◽  
Acetoxymethyl Ester ◽  
Dose Dependent

The physiological role of oxytocin (OT) in the kidney is still unclear, although autoradiographic data have shown the existence of OT receptors in the rat kidney. We examined the effect of OT in the microperfused rabbit cortical collecting duct (CCD) by using conventional cable analysis and microscope photometry. On addition of 10(-9) M OT to the bath, the lumen-negative transepithelial voltage (VT) transiently increased and the transepithelial resistance (RT) and the fractional resistance of the apical membrane (FRA) (1st phase) both decreased. After this initial change, the lumen-negative VT gradually decreased below its baseline level and RT and FRA (second phase) both increased. These electrical changes were dose dependent and were prevented by the addition of 10(-5) M amiloride to the lumen. Although responses to OT were not prevented by 10(-9) M arginine vasopressin (AVP) or 10(-6) M of a V1-receptor antagonist (OPC-21268) or V2-receptor antagonist (OPC-31260), they were inhibited by the addition of the specific OT antagonist des-Gly-NH2-[d(CH2)3,Tyr(Me),Thr]OVT. Additional studies of intracellular free calcium ([Ca2+]i) revealed that 10(-8)-10(-6) M OT caused an increase in [Ca2+]i in CCD in a dose-dependent manner. Also, pretreatment with 2 x 10(-8) M bis-(aminophenoxy)ethane-tetraacetic acid-acetoxymethyl ester, an intracellular Ca2+ chelator, abolished the electrical and [Ca2+]i responses to OT. Pretreatment with 5 x 10(-4) M 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (CPT-cAMP) partially prevented the electrical responses to OT, thus reducing the decrease in lumen-negative VT below its basal level and the increase in RT after the 1st phase. These data show that OT affects the apical Na+ conductance of collecting duct cells through OT receptors distinct from the AVP receptors and that the effect of OT may, at least in part, be brought about by a mechanism(s) dependent on the increase in [Ca2+]i and cAMP production.

Prostaglandin transporter PGT is expressed in cell types that synthesize and release prostanoids

2002 ◽  
Vol 282 (6) ◽  
pp. F1103-F1110 ◽  
Author(s):  
Yi Bao ◽  
Michael L. Pucci ◽  
Brenda S. Chan ◽  
Run Lu ◽  
Shigekazu Ito ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Mesangial Cells ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Cell Types ◽  
Proximal Tubules ◽  
Surface Epithelium ◽  
Extracellular Loop ◽  
Insight Into ◽  
Rat Platelets

PGT is a broadly expressed transporter of prostaglandins (PGs) and thromboxane that is energetically poised to take up prostanoids across the plasma membrane. To gain insight into the function of PGT, we generated mouse monoclonal antibody 20 against a portion of putative extracellular loop 5 of rat PGT. Immunoblots of endogenous PGT in rat kidney revealed a 65-kDa protein in a zonal pattern corresponding to PG synthesis rates (papilla ≅ medulla > cortex). Immunocytochemically, PGT in rat kidneys was expressed in glomerular endothelial and mesangial cells, arteriolar endothelial and muscularis cells, principal cells of the collecting duct, medullary interstitial cells, medullary vasa rectae endothelia, and papillary surface epithelium. Proximal tubules, which are known to take up and metabolize PGs, were negative. Immunoblotting and immunocytochemistry revealed that rat platelets also express abundant PGT. Coexpression of the PG synthesis apparatus (cyclooxygenase) and PGT by the same cell suggests that prostanoids may undergo release and reuptake.

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.

Minealocorticoid receptors and 11 beta-steroid dehydrogenase activity in renal principal and intercalated cells

1994 ◽  
Vol 266 (1) ◽  
pp. F76-F80 ◽  
Author(s):  
A. Naray-Fejes-Toth ◽  
E. Rusvai ◽  
G. Fejes-Toth
Keyword(s):  
Cell Sorting ◽  
Direct Action ◽  
Collecting Duct ◽  
Cell Types ◽  
Target Cells ◽  
Intercalated Cells ◽  
Cortical Collecting Duct ◽  
Specific Receptors ◽  
Principal And Intercalated Cells ◽  
Steroid Dehydrogenase

Aldosterone exerts complex effects on the cortical collecting duct (CCD): it increases Na+ and K+ transport, and it also influences H+ and HCO3 transport. Whether these latter effects represent direct action of aldosterone on intercalated cells (ICC) or are secondary to changes in the transport of other electrolytes is unclear. Because the presence of specific receptors is the prerequisite of a direct steroid action, and mineralocorticoid receptors (MR) have not yet been demonstrated in ICC, in this study we determined the density of MR directly in isolated principal cells (PC) and beta-ICC. Purified populations of these two cell types were obtained from rabbit renal cortex by immunodissection and fluorescence-activated cell sorting. We found that both PC and beta-ICC contained a significant number of MR, although receptor density was higher in PC than in beta-ICC (6,704 +/- 912 vs. 2,181 +/- 388 MR sites/cell; P < 0.001). 11 beta-Hydroxysteroid dehydrogenase (11 beta-OHSD), an enzyme that is present predominantly in mineralocorticoid target cells, exhibited a distribution similar to that of MR in the two cell types. 11 beta-OHSD activity, determined by measuring the rate of conversion of [3H]corticosterone to 11-dehydrocorticosterone, was 1.08 +/- 0.14 and 0.34 +/- 0.08 fmol.min-1 x 1,000 cells-1 (P < 0.001) in intact PC and beta-ICC, respectively. 11 beta-OHSD in both cell types utilized NAD as cofactor. These results suggest that beta-ICC are potential direct targets of aldosterone and that MR in both PC and beta-ICC are protected by 11 beta-OHSD.

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