K
            +
            homeostasis is maintained with knockdown of big‐conductance K
            +
            channel in principal cells of connecting tubule/collecting duct

Within the CCD of the distal nephron of the rabbit, the BK (maxi K) channel mediates Ca2+- and/or stretch-dependent flow-induced K+ secretion (FIKS) and contributes to K+ adaptation in response to dietary K+ loading. An unresolved question is whether BK channels in intercalated cells (ICs) and/or principal cells (PCs) in the CCD mediate these K+ secretory processes. In support of a role for ICs in FIKS is the higher density of immunoreactive apical BKα (pore-forming subunit) and functional BK channel activity than detected in PCs, and an increase in IC BKα expression in response to a high-K+ diet. PCs possess a single apical cilium which has been proposed to serve as a mechanosensor; direct manipulation of cilia leads to increases in cell Ca2+ concentration, albeit of nonciliary origin. Immunoperfusion of isolated and fixed CCDs isolated from control K+-fed rabbits with channel subunit-specific antibodies revealed colocalization of immunodetectable BKα- and β1-subunits in cilia as well as on the apical membrane of cilia-expressing PCs. Ciliary BK channels were more easily detected in rabbits fed a low-K+ vs. high-K+ diet. Single-channel recordings of cilia revealed K+ channels with conductance and kinetics typical of the BK channel. The observations that 1) FIKS was preserved but 2) the high-amplitude Ca2+ peak elicited by flow was reduced in microperfused CCDs subject to pharmacological deciliation suggest that cilia BK channels do not contribute to K+ secretion in this segment, but that cilia serve as modulators of cell signaling.

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Expression of protein kinase C isoenzymes α, βI, and δ in subtypes of intercalated cells of mouse kidney

AJP Renal Physiology ◽

10.1152/ajprenal.00016.2006 ◽

2006 ◽

Vol 291 (5) ◽

pp. F1052-F1060 ◽

Cited By ~ 11

Author(s):

Wan-Young Kim ◽

Joon-Ho Jung ◽

Eun-Young Park ◽

Chul-Woo Yang ◽

Hyang Kim ◽

...

Keyword(s):

Collecting Duct ◽

Apical Part ◽

Mouse Kidney ◽

Intercalated Cells ◽

Principal Cells ◽

Connecting Tubule ◽

Intercalated Cell ◽

Tubule Cells ◽

Pkc Β ◽

Calbindin D

Recent studies of the distribution of PKC isoenzymes in the mouse kidney demonstrated that PKC-α, -βI, and -δ are expressed in intercalated cells. The purpose of this study was to identify the intercalated cell subtypes that express the different PKC isoenzymes and determine the location of the PKC isoenzymes within these cells. Adult C57BL/6 mice kidney tissues were processed for multiple-labeling immunohistochemistry. Antibodies against the vacuolar H+-ATPase and pendrin were used to identify intercalated cell subtypes, whereas antibodies against calbindin D28K and aquaporin-2 (AQP2) were used to identify connecting tubule cells and principal cells of the collecting duct, respectively. Within type A intercalated cells, PKC-δ was highly expressed in the apical part of the cells, whereas immunoreactivity for both PKC-α and PKC-βI was weak. Type B intercalated cells exhibited strong expression of PKC-α, -βI, and -δ. PKC-α and -βI were localized throughout the cytoplasm, whereas PKC-δ was restricted to the basal domain. Within non-A-non-B cells, immunoreactivity for both PKC-α and PKC-βI was high in intensity and localized diffusely in the cytoplasm, whereas PKC-δ was localized in the apical part of the cells. None of the PKC isoenzymes (PKC-α, -βI, or -δ) were expressed in the calbindin D28K-positive connecting tubule cells. Within AQP2-positive principal cells of the collecting duct, PKC-α was expressed on the basolateral plasma membrane, but no significant staining was detected for PKC-βI and -δ. In summary, this study demonstrates distinct and differential expression patterns of PKC-α, -βI, and -δ in the three subtypes of intercalated cells in the mouse kidney.

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Vasopressin increases density of apical low-conductance K+ channels in rat CCD

AJP Renal Physiology ◽

10.1152/ajprenal.1993.264.3.f502 ◽

1993 ◽

Vol 264 (3) ◽

pp. F502-F509 ◽

Cited By ~ 19

Author(s):

A. C. Cassola ◽

G. Giebisch ◽

W. Wang

Keyword(s):

Collecting Duct ◽

Phosphodiesterase Inhibitor ◽

K Channel ◽

Channel Activity ◽

Dibutyryl Camp ◽

Open Probability ◽

Simultaneous Application ◽

K Channels ◽

Principal Cells ◽

High K

The effect of arginine vasopressin (AVP) on the low-conductance K+ channel in the apical membrane of rat cortical collecting duct (CCD) principal cells from animals on a control and high-K+ diet was studied using patch-clamp techniques. AVP stimulated apical low-conductance K+ channel activity in both control and high-K+ animals: application of 110-220 pM AVP induced a significant increase in the density of low-conductance K+ channels. In the presence of phosphodiesterase inhibitor (3-isobutyl-1-methylxanthine), administration of 22 pM AVP also increased channel activity. The action of AVP on low-conductance K+ channel activity was mimicked by simultaneous application of forskolin and 3-isobutyl-1-methylxanthine. Exogenously applied N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate (dibutyryl-cAMP, 0.4-0.8 mM) also increased apical low-conductance K+ channel activity. Since channel open probability (Po) was almost saturated in the absence of AVP, the increase of channel activity induced by AVP, forskolin, and dibutyryl-cAMP resulted predominantly from stimulating previously silent K+ channels. We conclude that AVP induces an increase of low-conductance K+ channel activity of principal cells in rat CCD by the stimulation of cAMP-dependent protein kinase. The AVP-induced increase of low-conductance K+ channel activity can thus significantly contribute to the hormone-induced K+ secretion in the rat CCD.

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Aquaporin-4 Expression in Adult and Developing Mouse and Rat Kidney

Journal of the American Society of Nephrology ◽

10.1681/asn.v1291795 ◽

2001 ◽

Vol 12 (9) ◽

pp. 1795-1804

Author(s):

YOUNG-HEE KIM ◽

JAE-HO EARM ◽

TONGHUI MA ◽

ALAN S. VERKMAN ◽

MARK A. KNEPPER ◽

...

Keyword(s):

Proximal Tubule ◽

Kidney Development ◽

Collecting Duct ◽

Rat Kidney ◽

Aquaporin 4 ◽

Principal Cells ◽

Connecting Tubule ◽

S3 Segment ◽

Medullary Collecting Duct ◽

Old Mice

Abstract. Aquaporin-4 (AQP4) is a member of the aquaporin water-channel family. AQP4 is expressed primarily in the brain, but it is also present in the collecting duct of the kidney, where it is located in the basolateral plasma membrane of principal cells and inner medullary collecting duct (IMCD) cells. Recent studies in the mouse also have reported the presence of AQP4 in the basolateral membrane of the proximal tubule. The purpose of this study was to establish the pattern of AQP4 expression during kidney development and in the adult kidney of both the mouse and the rat. Kidneys of adult and 3-, 7-, and 15-d-old mice and rats were preserved for immunohistochemistry and processed using a peroxidase pre-embedding technique. In both the mouse and the rat, strong basolateral immunostaining was observed in IMCD cells and principal cells in the medullary collecting duct at all ages examined. Labeling was weaker in the cortical collecting duct and the connecting tubule, and there was no labeling of connecting tubule cells in the mouse. In adult mouse kidney, strong AQP4 immunoreactivity was observed in the S3 segment of the proximal tubule. However, there was little or no labeling in the cortex or around the corticomedullary junction in 3- and 7-d-old mice. Between 7 and 15 d of age, distinct AQP4 immunoreactivity appeared in the S3 segment of the mouse proximal tubule concomitant with the differentiation of this segment of the nephron. Labeling of proximal tubules was never observed in the rat kidney. These results suggest that there are differences in transepithelial water transport between mouse and rat or that additional, not yet identified water channels exist in the rat proximal tubule.

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Immunoelectron microscopic localization of NBC3 sodium-bicarbonate cotransporter in rat kidney

AJP Renal Physiology ◽

10.1152/ajprenal.2000.278.2.f327 ◽

2000 ◽

Vol 278 (2) ◽

pp. F327-F336 ◽

Cited By ~ 42

Author(s):

Tae-Hwan Kwon ◽

Alexander Pushkin ◽

Natalia Abuladze ◽

Søren Nielsen ◽

Ira Kurtz

Keyword(s):

Plasma Membrane ◽

Immunoelectron Microscopy ◽

Collecting Duct ◽

Rat Kidney ◽

Type A ◽

Apical Plasma Membrane ◽

Type B ◽

Principal Cells ◽

Connecting Tubule ◽

Basolateral Plasma Membrane

In the present study, we produced a rabbit peptide-derived polyclonal COOH-terminal antibody that selectively recognizes NBC3, to determine the cellular and subcellular localization of NBC3 in rat kidney, using immunocytochemistry and immunoelectron microscopy. Immunocytochemistry with cryostat sections and semithin cryosections revealed specific staining of intercalated cells (ICs) in the connecting tubule and in cortical, outer medullary, and initial inner medullary collecting ducts. In the connecting tubule and in the cortical and medullary collecting duct, the labeling was associated with both type A and type B ICs. In type A ICs, labeling was confined to the apical and subapical domains, whereas in type B ICs, basal domains were exclusively labeled. In contrast, collecting duct principal cells were consistently unlabeled, and this was confirmed using anti-aquaporin-2 antibodies, which labeled principal cells in parallel semithin cryosections. Glomeruli, proximal tubules, descending thin limbs, ascending thin limbs, thick ascending limbs, distal convoluted tubules, and vascular structures were unlabeled. For immunoelectron microscopy, tissue samples were freeze-substituted, and immunolabeling was performed on ultrathin Lowicryl HM20 sections. Immunoelectron microscopy demonstrated that NBC3 labeling was very abundant in the apical plasma membrane, in intracellular vesicles, and in tubulocisternal profiles in the subapical domains of type A ICs. In type B ICs, NBC3 was mainly present in the basolateral plasma membrane. Immunolabeling controls using peptide-absorbed antibody were consistently negative. In conclusion, NBC3 is highly abundant in the apical plasma membrane of type A ICs and in the basolateral plasma membrane of type B ICs. This suggests that NBC3 plays an important role in modulating bicarbonate transport in the connecting tubule and collecting duct.

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With-No-Lysine Kinase 1 (WNK1) Augments TRPV4 Function in the Aldosterone-Sensitive Distal Nephron

Cells ◽

10.3390/cells10061482 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1482

Author(s):

Viktor N. Tomilin ◽

Kyrylo Pyrshev ◽

Naghmeh Hassanzadeh Khayyat ◽

Oleg Zaika ◽

Oleh Pochynyuk

Keyword(s):

Collecting Duct ◽

Chinese Hamster ◽

Dominant Negative ◽

K Channel ◽

Apical Plasma Membrane ◽

Dependent Manner ◽

Distal Nephron ◽

Potassium Homeostasis ◽

Wnk Kinases ◽

K Secretion

Kidneys play a central role in regulation of potassium homeostasis and maintenance of plasma K+ levels within a narrow physiological range. With-no-lysine (WNK) kinases, specifically WNK1 and WNK4, have been recognized to regulate K+ balance, in part, by orchestrating maxi K+ channel (BK)-dependent K+ secretion in the aldosterone-sensitive distal nephron (ASDN), which includes the connecting tubule and collecting duct. We recently demonstrated that the Ca2+-permeable TRPV4 channel is essential for BK activation in the ASDN. Furthermore, high K+ diet increases TRPV4 activity and expression largely in an aldosterone-dependent manner. In the current study, we aimed to test whether WNK kinases contribute to regulation of TRPV4 activity and its stimulation by aldosterone. Systemic inhibition of WNK with WNK463 (1 mg/kgBW for 3 days) markedly decreased TRPV4-dependent Ca2+ influx in freshly isolated split-opened collecting ducts. Aldosterone greatly increased TRPV4 activity and expression in cultured mpkCCDc14 cells and this effect was abolished in the presence of WNK463. Selective inhibition of WNK1 with WNK-in-11 (400 nM, 24 h) recapitulated the effects of WNK463 on TRPV4-dependent Ca2+ influx. Interestingly, WNK-in-11 did not interfere with up-regulation of TRPV4 expression by aldosterone, but prevented translocation of the channel to the apical plasma membrane. Furthermore, co-expression of TRPV4 and WNK1 into Chinese hamster ovary (CHO) cells increased the macroscopic TRPV4-dependent cation currents. In contrast, over-expression of TRPV4 with a dominant negative WNK1 variant (K233M) decreased the whole-cell currents, suggesting both stimulatory and permissive roles of WNK1 in regulation of TRPV4 activity. Overall, we show that WNK1 is essential for setting functional TRPV4 expression in the ASDN at the baseline and in response to aldosterone. We propose that this new mechanism contributes to regulation of K+ secretion and, by extension, urinary K+ levels to maintain systemic potassium homeostasis.

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Vasopressin/V2 receptor stimulates renin synthesis in the collecting duct

AJP Renal Physiology ◽

10.1152/ajprenal.00360.2015 ◽

2016 ◽

Vol 310 (4) ◽

pp. F284-F293 ◽

Cited By ~ 18

Author(s):

Alexis A. Gonzalez ◽

Flavia Cifuentes-Araneda ◽

Cristobal Ibaceta-Gonzalez ◽

Alex Gonzalez-Vergara ◽

Leonardo Zamora ◽

...

Keyword(s):

Collecting Duct ◽

Critical Role ◽

Combined Treatment ◽

Receptor Activation ◽

Ang Ii ◽

Principal Cells ◽

Protein Levels ◽

Renin Synthesis ◽

Renin Mrna ◽

Creb Pathway

Renin is synthesized in the principal cells of the collecting duct (CD), and its production is increased via cAMP in angiotensin (ANG) II-dependent hypertension, despite suppression of juxtaglomerular (JG) renin. Vasopressin, one of the effector hormones of the renin-angiotensin system (RAS) via the type 2-receptor (V2R), activates the cAMP/PKA/cAMP response element-binding protein (CREB) pathway and aquaporin-2 expression in principal cells of the CD. Accordingly, we hypothesized that activation of V2R increases renin synthesis via PKA/CREB, independently of ANG II type 1 (AT1) receptor activation in CD cells. Desmopressin (DDAVP; 10−6 M), a selective V2R agonist, increased renin mRNA (∼3-fold), prorenin (∼1.5-fold), and renin (∼2-fold) in cell lysates and cell culture media in the M-1 CD cell line. Cotreatment with DDAVP+H89 (PKA inhibitor) or CREB short hairpin (sh) RNA prevented this response. H89 also blunted DDAVP-induced CREB phosphorylation and nuclear localization. In 48-h water-deprived (WD) mice, prorenin-renin protein levels were increased in the renal inner medulla (∼1.4- and 1.8-fold). In WD mice treated with an ACE inhibitor plus AT1 receptor blockade, renin mRNA and prorenin protein levels were still higher than controls, while renin protein content was not changed. In M-1 cells, ANG II or DDAVP increased prorenin-renin protein levels; however, there were no further increases by combined treatment. These results indicate that in the CD the activation of the V2R stimulates renin synthesis via the PKA/CREB pathway independently of RAS, suggesting a critical role for vasopressin in the regulation of renin in the CD.

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Effect of aldosterone on the regulation of the volume of principal cells of rat cortical collecting duct epithelium in early postnatal development

Doklady Biological Sciences ◽

10.1134/s0012496608060057 ◽

2008 ◽

Vol 423 (1) ◽

pp. 385-388 ◽

Cited By ~ 2

Author(s):

N. S. Logvinenko ◽

E. I. Solenov ◽

L. N. Ivanova

Keyword(s):

Postnatal Development ◽

Collecting Duct ◽

Cortical Collecting Duct ◽

Early Postnatal Development ◽

Principal Cells ◽

Duct Epithelium ◽

Collecting Duct Epithelium

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Involvement of actin cytoskeleton in modulation of apical K channel activity in rat collecting duct

AJP Renal Physiology ◽

10.1152/ajprenal.1994.267.4.f592 ◽

1994 ◽

Vol 267 (4) ◽

pp. F592-F598 ◽

Cited By ~ 13

Author(s):

W. H. Wang ◽

A. Cassola ◽

G. Giebisch

Keyword(s):

Actin Cytoskeleton ◽

Actin Filaments ◽

Cytochalasin B ◽

Collecting Duct ◽

K Channel ◽

Cortical Collecting Duct ◽

Channel Activity ◽

Patch Clamp Technique ◽

Channel Inhibition ◽

Inside Out

We have employed the patch-clamp technique to investigate the role of the actin cytoskeleton in the modulation of the low-conductance K+ channel in the apical membrane of the rat cortical collecting duct (CCD). This K+ channel is inactivated by application of cytochalasin B or D, both compounds known to disrupt actin filaments. The effect of both cytochalasins, B and D, was fully reversible in cell-attached patches, but channel activity could not be fully restored in excised membrane patches. The effect of cytochalasins on channel activity was specific and resulted from depolymerization of the actin cytoskeleton, since application of 10 microM chaetoglobosin C, a cytochalasin analogue that does not depolymerize the actin filaments, had no effect on channel activity in inside-out patches. Addition of either actin monomers or of the polymerizing actin filaments in inside-out patches to the cytosolic medium had no effect on channel activity. This suggests that cytochalasin B- or D-induced inactivation of apical K+ channels is not caused by obstruction of the channel pore by actin. We also observed that channel inhibition by cytochalasin B or D could be blocked by pretreatment with 5 microM phalloidin, a compound that stabilizes actin filaments. We conclude that apical K+ channel activity depends critically on the integrity of the actin cytoskeleton.

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