Cl− channels of the distal nephron

2006 ◽  
Vol 291 (6) ◽  
pp. F1157-F1168 ◽  
Author(s):  
Lawrence G. Palmer ◽  
Gustavo Frindt
Keyword(s):  
Voltage Dependence ◽  
Collecting Duct ◽  
Anion Channel ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
Solute Depletion ◽  
Fluid Layers ◽  
Cl Channels ◽  
Current Transients

Cl− currents were observed under whole cell clamp conditions in cells of the rat cortical collecting duct (CCD), connecting tubule (CNT), and thick ascending limb of Henle's loop (TALH). These currents were much larger in intercalated cells compared with principal cells of the CCD and were also larger in the TALH and in the CNT compared with the CCD. The conductance had no strong voltage dependence, and steady-state currents were similar in inward and outward directions with similar Cl− concentrations on both sides of the membrane. Current transients were observed, particularly at low Cl− concentrations, which could be explained by solute depletion and concentration in fluid layers next to the membrane. The currents had a remarkable selectivity among anions. Among halides, Br− and F− conductances were only 15% of that of Cl−, and I− conductance was immeasurably small. SCN− and OCN− conductances were ∼50%, and aspartate, glutamate, and methanesulfonate conductance was ∼5% that of Cl−. No conductance could be measured for any other anion tested, including NO3−, HCO3−, formate, acetate, or isethionate; NO3− and I− appeared to block the channels weakly. Conductances were diminished by lowering the extracellular pH to 6.4. The properties of the conductance fit best with those of the cloned renal anion channel ClC-K2 and likely reflect the basolateral Cl− conductances of the cells of these nephron segments.

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.

Different mechanisms of renal Na-K-ATPase regulation by protein kinases in proximal and distal nephron

1993 ◽  
Vol 265 (3) ◽  
pp. F399-F405 ◽  
Author(s):  
T. Satoh ◽  
H. T. Cohen ◽  
A. I. Katz
Keyword(s):  
Arachidonic Acid ◽  
Protein Kinase ◽  
Collecting Duct ◽  
Common Mechanism ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
Inhibitory Peptide ◽  
Medullary Thick Ascending Limb ◽  
Pump Activity

We recently reported a novel intracellular mechanism of Na-K-adenosinetriphosphatase (Na-K-ATPase) regulation in the cortical collecting duct (CCD) by agents that increase cell adenosine 3',5'-cyclic monophosphate (cAMP), which involves stimulation of protein kinase A (PKA) and phospholipase A2 (PLA2). We now determined whether this mechanism also operates in other nephron segments. In the medullary thick ascending limb (MTAL) dopamine, the DA1 agonist fenoldopam, forskolin, or dibutyryl-cAMP inhibited Na-K-ATPase activity, similar to results in CCD. In both segments this effect was blocked by 20-residue inhibitory peptide (IP20), a peptide inhibitor of PKA, but not by staurosporine, a protein kinase C (PKC) inhibitor. PKC activators phorbol 12-myristate 13-acetate, phorbol 12,13-dibutyrate, and 1,2-myristate 13-acetate, phorbol 12,13-dibutyrate, and 1,2-dioctanoylglycerol had no effect on Na-K pump activity in either CCD or MTAL. In contrast, all three PKC activators inhibited pump activity in the proximal convoluted tubule (PCT), an effect reproduced only by dopamine or by parathyroid hormone [PTH-(1-34)]. In PCT the pump inhibition by dopamine or PTH-(1-34) was abolished by staurosporine but not by IP20. The PLA2 inhibitor mepacrine prevented the effect of all agents, and arachidonic acid produced a dose-dependent pump inhibition in each of the three segments studied. We conclude that intracellular mechanisms of Na-K-ATPase regulation differ along the nephron, as they involve activation of PKA in CCD and MTAL and of PKC in PCT. These two pathways probably share a common mechanism in stimulating PLA2, arachidonic acid release, and production of eicosanoids in both the proximal and distal nephron.

Localization of connexin 30 in the luminal membrane of cells in the distal nephron

2005 ◽  
Vol 289 (6) ◽  
pp. F1304-F1312 ◽  
Author(s):  
Fiona McCulloch ◽  
Régine Chambrey ◽  
Dominique Eladari ◽  
János Peti-Peterdi
Keyword(s):  
Gap Junction ◽  
Collecting Duct ◽  
Protein A ◽  
High Salt ◽  
Rabbit Kidney ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
Luminal Membrane ◽  
Junction Protein

Several isoforms of the gap junction protein connexin (Cx) have been identified in a variety of tissues that communicate intercellular signals between adjacent cells. In the kidney, Cx37, Cx40, and Cx43 are localized in the vasculature, glomerulus, and tubular segments in a punctuate pattern, typical of classic gap junction channels. We performed immunohistochemistry in the mouse, rat, and rabbit kidney to study the localization of Cx30 protein, a new member of the Cx family. The vasculature, glomerulus, and proximal nephron segments were devoid of staining in all three species. Unexpectedly, Cx30 was found throughout the luminal membrane of select cells in the distal nephron. Expression of Cx30 was highest in the rat, which also showed some diffuse cytosolic labeling, continuous from the medullary thick ascending limb to the collecting duct system, and with the highest level in the distal convoluted tubule. Labeling in the mouse and rabbit was much less, limited to intercalated cells in the connecting segment and cortical collecting duct, where the apical signal was particularly strong. A high-salt-containing diet and culture medium upregulated Cx30 expression in the rat inner medulla and in M1 cells, respectively. The distinct, continuous labeling of the luminal plasma membrane and upregulation by high salt suggest that Cx30 may function as a hemichannel involved in the regulation of salt reabsorption in the distal nephron.

Cl− channels in basolateral renal medullary membranes XII. Anti-rbClC-Ka antibody blocks MTAL Cl−channels

1997 ◽  
Vol 273 (6) ◽  
pp. F1030-F1038 ◽  
Author(s):  
Christopher J. Winters ◽  
Ludwika Zimniak ◽  
W. Brian Reeves ◽  
Thomas E. Andreoli
Keyword(s):  
Lipid Bilayers ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Rabbit Kidney ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Patch Clamp Technique ◽  
Medullary Thick Ascending Limb ◽  
Acid Fragment ◽  
Cl Channels

Cl− channels in the medullary thick ascending limb (MTAL) studied by either patch-clamp technique or reconstitution into lipid bilayers are activated by increases in intracellular Cl−concentrations. rbClC-Ka, a ClC Cl− channel, may represent this channel. We therefore evaluated the role of rbClC-Ka in transcellular MTAL Cl− transport in two separate ways. First, an antibody was raised against a fusion protein containing a 153-amino acid fragment of rbClC-Ka. Immunostaining of rabbit kidney sections with the antibody was localized to basolateral regions of MTAL and cortical thick ascending limb (CTAL) segments and also to the cytoplasm of intercalated cells in the cortical collecting duct. Second, Cl− uptake and efflux were measured in suspensions of mouse MTAL segments. Cl− uptake was bumetanide sensitive and was stimulated by treatment with a combination of vasopressin + forskolin + dibutyryl adenosine 3′,5-cyclic monophosphate (DBcAMP). Cl− efflux was also increased significantly by vasopressin + forskolin + DBcAMP from 114 ± 20 to 196 ± 36 nmol ⋅ mg protein−1 ⋅ 45 s−1( P = 0.003). Cl− efflux was inhibited by the Cl− channel blocker diphenylamine-2-carboxylate (154 ± 26 vs. 70 ± 21 nmol ⋅ mg protein−1 ⋅ 45 s−1, P = 0.003). An anti-rbClC-Ka antibody, which inhibits the activity of MTAL Cl− channels in lipid bilayers, reduced Cl− efflux from intact MTAL segments (154 ± 28 vs. 53 ± 14 nmol ⋅ mg protein−1 ⋅ 45 s−1, P = 0.02). These results support the view that rbClC-Ka is the basolateral membrane Cl− channel that mediates vasopressin-stimulated net Cl− transport in the MTAL segment.

Mechanism of PGE2-induced cell swelling in distal nephron segments

1992 ◽  
Vol 263 (5) ◽  
pp. F824-F832
Author(s):  
T. Shimizu ◽  
M. Naruse ◽  
M. Takeda ◽  
M. Nakamura ◽  
K. Yoshitomi ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Cell Swelling ◽  
Rabbit Kidney ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
Nephron Segments ◽  
Pg E2 ◽  
Dose Dependent ◽  
Sustained Increase

The effects of prostaglandin (PG) E2 on cell swelling were studied in isolated perfused tubules of rabbit kidney. PGE2 (1 microM) added to the bath induced cell swelling by 13.4, 7.2, and 9.6% in the connecting tubule, distal convoluted tubule, and cortical collecting duct, respectively, but it had no effect on the proximal convoluted tubule and cortical thick ascending limb. The response was dose dependent in the range of 1 nM to 1 microM. PGI2 exerted a similar effect, but PGF2 alpha had no effect. The swelling was completely blocked by basolateral Na+ removal and was attenuated by bilateral Cl- removal, suggesting that the swelling was mediated by basolateral Na+ entry in association with Cl- entry. In all segments except proximal tubule, PGE2 caused an initial transient peak followed by a sustained increase in intracellular Ca2+. Intracellular Ca2+ chelation or inhibition of Ca2+ release from intracellular stores abolished the PGE2-induced cell swelling, but extracellular Ca2+ removal did not. An inhibitor of the Na(+)-Ca2+ exchanger (3',4'-dichlorobenzamil, 100 microM) in the bath completely inhibited PGE2-induced cell swelling. Neither furosemide (1 mM) nor amiloride (1 mM) added to bath abolished the response, indicating that neither Na(+)-K(+)-2Cl- cotransport nor Na(+)-H+ exchange is involved in the action of PGE2. The swelling response to PGE2 was observed even in the presence of ouabain, indicating that the effect of PGE2 is independent of Na(+)-K(+)-adenosinetriphosphatase inhibition. Nicardipine added to bath partially inhibited the swelling response.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid phosphatase activity in the mammalian nephron

1984 ◽  
Vol 247 (2) ◽  
pp. F252-F259 ◽  
Author(s):  
C. J. Olbricht ◽  
L. C. Garg ◽  
J. K. Cannon ◽  
C. C. Tisher
Keyword(s):  
Acid Phosphatase ◽  
Proximal Tubule ◽  
Collecting Duct ◽  
Rabbit Kidney ◽  
Male Rat ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
S3 Segment ◽  
Medullary Collecting Duct

Lysosomal acid phosphatase (AcPase) activity was measured in individual segments of rat and rabbit nephrons employing 4-methylumbelliferyl phosphate as the substrate. Generation of reaction product was linear with incubation time up to 127 min and with tubule length. Activity was much higher in glomeruli and proximal tubules of rat than rabbit kidney. In both rat and rabbit there were higher activities in juxtamedullary than in superficial glomeruli. In rats, AcPase activity decreased from S1 to S3 segments, which parallels the known decrease in the number of lysosomes. Surprisingly, in rabbits of both sexes AcPase activity in the cortical collecting duct (CCD), which contains a limited number of lysosomes, was comparable to levels measured in the S1 and S2 segments of the proximal tubule. Similarly, in the male rat values for AcPase activity in the cortical thick ascending limb, distal convoluted tubule, CCD, and medullary collecting duct paralleled those in the S3 segment. These findings suggest that a considerable amount of AcPase in the distal nephron is either extralysosomal or that the amount of lysosomal AcPase activity per unit volume is greater in distal nephron segments compared with the proximal tubule. Different K'm values for AcPase in S1 segments and CCD were found in the rabbit, suggesting the presence of different isoenzymes.

Calcium transport across segments of the rabbit distal nephron in vitro

1978 ◽  
Vol 235 (4) ◽  
pp. F367-F375 ◽  
Author(s):  
G. R. Shareghi ◽  
L. C. Stoner
Keyword(s):  
Calcium Absorption ◽  
Collecting Duct ◽  
Cyclic Adenosine Monophosphate ◽  
Adenosine Monophosphate ◽  
Passive Movement ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
K Secretion

The mechanism of Ca2+ transport by various segments of the distal nephron was studied in vitro using the isolated perfused tubule technique. Calcium absorption in the distal convoluted tubule (DCT) and the granular portion of the cortical collecting duct (CCTg) was significantly enhanced in the presence of parathyroid hormone (PTH), 3 X 10(-2) U/ml. Na+ was absorbed from and K+ was secreted into the lumen of the DCT. The presence of amiloride (5 X 10(-5) M) or furosemide (5 X 10(-5) M) in the perfusate of DCT each caused a partial inhibition of Na+ but not Ca2+ absorption. The foregoing result with Na+ is consistent with the heterogeneous nature of DCT. Net Na+ absorption and K+ secretion also occurred in the CCTg; both processes were completely inhibited by amiloride. Ca2+ absorption occurred in the thick ascending limb of Henle's loop; it was not enhanced by PTH, and the results were consistent with passive movement. No net Ca2+ movement was observed in the nongranular (light) segment of the cortical collecting tubule in the presence or absence of PTH or dibutyryl cyclic adenosine monophosphate.

Low Na intake suppresses expression of CYP2C23 and arachidonic acid-induced inhibition of ENaC

2006 ◽  
Vol 291 (6) ◽  
pp. F1192-F1200 ◽  
Author(s):  
Peng Sun ◽  
Dao-Hong Lin ◽  
Tong Wang ◽  
Elisa Babilonia ◽  
Zhijian Wang ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Collecting Duct ◽  
Inhibitory Effect ◽  
Thick Ascending Limb ◽  
Epoxyeicosatrienoic Acid ◽  
Distal Nephron ◽  
Na Transport ◽  
Deficient Diet ◽  
Epithelial Na Channels ◽  
Clamp Study

We previously demonstrated that arachidonic acid (AA) inhibits epithelial Na channels (ENaC) through the cytochrome P-450 (CYP) epoxygenase-dependent pathway ( 34 ). In the present study, we tested the hypothesis that low Na intake suppresses the expression of CYP2C23, which is mainly responsible for converting AA to epoxyeicosatrienoic acid (EET) in the kidney ( 11 ) and attenuates the AA-induced inhibition of ENaC. Immunostaining showed that CYP2C23 is expressed in the Tamm-Horsfall protein (THP)-positive and aquaporin 2 (AQP2)-positive tubules. This suggests that CYP2C23 is expressed in the thick ascending limb (TAL) and collecting duct (CD). Na restriction significantly suppressed the expression of CYP2C23 in the TAL and CD. Western blot also demonstrated that the expression of CYP2C23 in renal cortex and outer medulla diminished in rats on Na-deficient diet (Na-D) but increased in those on high-Na diet (4%). Moreover, the content of 11,12-epoxyeicosatrienoic acid (EET) decreased in the isolated cortical CD from rats on Na-D compared with those on a normal-Na diet (0.5%). Patch-clamp study showed that application of 15 μM AA inhibited the activity of ENaC by 77% in the CCD of rats on a Na-D for 3 days. However, the inhibitory effect of AA on ENaC was significantly attenuated in rats on Na-D for 14 days. Furthermore, inhibition of CYP epoxygenase with MS-PPOH increased the ENaC activity in the CCD of rats on a control Na diet. We also used microperfusion technique to examine the effect of MS-PPOH on Na transport in the distal nephron. Application of MS-PPOH significantly increased Na absorption in the distal nephron of control rats but had no significant effect on Na absorption in rats on Na-D for 14 days. We conclude that low Na intake downregulates the activity and expression of CYP2C23 and attenuates the inhibitory effect of AA on Na transport.

Critical role of the mineralocorticoid receptor in aldosterone-dependent and aldosterone-independent regulation of ENaC in the distal nephron

2021 ◽  
Author(s):  
Viatcheslav Nesterov ◽  
Marko Bertog ◽  
Jérémie Canonica ◽  
Edith Hummler ◽  
Richard Coleman ◽  
...  
Keyword(s):  
Mineralocorticoid Receptor ◽  
Collecting Duct ◽  
Critical Role ◽  
Sodium Absorption ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
Patch Clamp Technique ◽  
Transition Zones ◽  
Rate Limiting Step

The epithelial sodium channel (ENaC) constitutes the rate-limiting step for sodium absorption in the aldosterone-sensitive distal nephron (ASDN) comprising the late distal convoluted tubule (DCT2), the connecting tubule (CNT) and the collecting duct. Previously, we demonstrated that ENaC activity in the DCT2/CNT transition zone is constitutively high and independent of aldosterone, in contrast to its aldosterone dependence in the late CNT and initial cortical collecting duct (CNT/CCD). The mineralocorticoid receptor (MR) is expressed in the entire ASDN. Its activation by glucocorticoids is prevented through 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) abundantly expressed in the late but probably not the early part of ASDN. We hypothesized that ENaC function in the early part of the ASDN is aldosterone-independent but may depend on MR activated by glucocorticoids due to low 11β-HSD2 abundance. To test this hypothesis, we used doxycycline-inducible nephron-specific MR-deficient mice (MR KO). Whole-cell ENaC currents were investigated in isolated nephron fragments from DCT2/CNT or CNT/CCD transition zones using the patch-clamp technique. ENaC activity was detectable in CNT/CCD of control mice but absent or barely detectable in the majority of CNT/CCD preparations from MR KO mice. Importantly, ENaC currents in DCT2/CNT were greatly reduced in MR KO mice compared to ENaC currents in DCT2/CNT of control mice. Immunofluorescence for 11β-HSD2 was abundant in CCD, less prominent in CNT and very low in DCT2. We conclude that MR is critically important for maintaining aldosterone-independent ENaC activity in DCT2/CNT. Aldosterone-independent MR activation is probably mediated by glucocorticoids due to low expression of 11β-HSD2.

scholarly journals RenalAT1Receptor Protein Expression During the Early Stage of Diabetes Mellitus

2002 ◽  
Vol 3 (2) ◽  
pp. 97-108 ◽  
Author(s):  
Lisa M. Harrison-Bernard ◽  
John D. Imig ◽  
Pamela K. Carmines
Keyword(s):  
Diabetes Mellitus ◽  
Protein Expression ◽  
Early Stage ◽  
Collecting Duct ◽  
Receptor Protein ◽  
Cortical Collecting Duct ◽  
Distal Nephron ◽  
Protein Levels ◽  
Nephron Segments

Experiments were performed to evaluate the hypothesis that the early stage of Type 1 diabetes mellitus (DM) increases renal angiotensin II (AngII) concentration and angiotensin type 1 (AT1) receptor protein levels. Nineteen or twenty days after vehicle (Sham rats) or streptozotocin (STZ rats) treatment, plasma [AngII] was higher in STZ rats (152±23 fmol/ml) than in Sham rats (101±7 fmol/ml); however, kidney [AngII] did not differ between groups.AT1receptor protein expression was greater in STZ kidneys than in Sham kidneys. This increase was restricted to the cortex, whereAT1protein levels were elevated by 77±26% (42 kDa) and 101±16% (58 kDa) in STZ kidneys. Immunohistochemistry revealed this effect to be most evident in distal nephron segments including the connecting tubule/cortical collecting duct. Increased renal corticalAT1receptor protein and circulating AngII levels are consistent with an exaggerated AngII-dependent influence on renal function during the early stage of DM in the rat.

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