Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P41181 (collecting duct)
 5,183 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Urinary obstruction markedly reduces collecting duct Na+ reabsorption. To define the cellular mechanisms of this derangement in Na+ reabsorption in inner medullary collecting duct (IMCD) of obstructed kidneys, suspensions of intact IMCD cells and inner medulla plasma membranes (IMPM) were prepared from 24 h obstructed and untreated control kidneys. Oxygen consumption (QO2) studies revealed marked reductions in both amiloride-sensitive and ouabain-sensitive QO2 but not ouabain-insensitive QO2 in intact IMCD cells from obstructed, compared with control animals, indicating a reduction in oxygen-dependent transport activities of both the Na+ channel and the Na(+)-K(+)-adenosinetriphosphatase (ATPase). Amiloride-sensitive conductive 22Na+ uptake in intact IMCD cells from obstructed kidneys was significantly decreased by 45% at 10 s, 30 s, and 1-5 min (10 s: 2.42 +/- 0.63 vs. 4.49 +/- 0.64 nmol Na+ flux/mg protein, n = 7, P < 0.05; 1 min: 4.65 +/- 0.7 vs. 8.27 +/- 0.98 nmol Na+ flux/mg protein, n = 7, P < 0.05), indicating decreased activity of amiloride-sensitive Na+ channels in these cells. However, immunoblots of IMPM with antibodies to Na+ channel proteins did not show significant differences in content of Na+ channel proteins between membranes from obstructed and control groups. Ouabain-sensitive Na(+)-K(+)-ATPase activity in IMPM of obstructed kidneys was also reduced (61.1 +/- 18.1 vs. 152.6 +/- 25.8 nmol ATP degradation.min-1.mg protein-1, n = 6, P < 0.02), and immunoblots with monoclonal antibodies against the alpha 1- and beta-subunits of rabbit Na(+)-K(+)-ATPase showed a 51 +/- 7% reduction of both subunits in IMPM from obstructed kidneys (n = 4).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Transport defects of rabbit inner medullary collecting duct cells in obstructive nephropathy. 838 52

This study describes the establishment of a rat kidney cortical collecting duct (CCD) clonal cell line (RCCD1 cells) that maintains high transepithelial resistance and specific hormonal sensitivities. Immortalized cells were obtained by infection of primary cultured CCD cells with the wild-type simian virus 40. Grown on Petri dishes, RCCD1 cells are organized as monolayers of cuboid cells separated by tight junctions and form domes. Grown on permeable filters, confluent RCCD1 cells exhibit high transepithelial resistance (Rt: 2390 +/- 140 omega. cm2), transepithelial potential difference (PD) of -10.5 +/- 1.2 mV lumen negative, an associated short-circuit current (Isc) of 4.3 +/- 0.5 microA/cm2, and generated significant Na+, K+, H+ and HCO3- gradients, reflecting Na+ and H+ reabsorption and K+ and HCO3- secretion. RCCD1 cells exhibit features of both principal (PC) and intercalated (IC) cells. Consistent with PC phenotype, about 50% of the cells were positively stained by a PC-specific agglutinin. In situ hybridization studies revealed the presence of alpha, beta and gamma subunit mRNAs of the amiloride-sensitive epithelial Na+ channel and alpha 1 and beta 1 subunits of Na(+)-K(+)-ATPase. Moreover, Na(+)-K(+)-ATPase was immunolocalized at the basolateral side of the cells. Arginine vasopressin (AVP) induced a significant increase in both cellular cAMP content and Isc. Amiloride decreased in a dose-dependent manner Isc from untreated and AVP-treated RCCD1 cells. In addition, a barium-sensitive K+ conductance was evidenced in the apical side of the cells. Consistent with IC phenotype, isoproterenol (ISO) provoked a large increase in cellular cAMP and stimulated Isc. The effect of ISO on Isc was blocked by 5 x 10(-3) M DPC, a chloride channel blocker. Finally, AVP plus ISO had additive effect on Isc. Taken together, these results provide evidence that the RCCD1 cell line has maintained many of the original properties of rat CCD from which they were derived.
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PMID:Characteristics of a rat cortical collecting duct cell line that maintains high transepithelial resistance. 884 Feb 62

Ontogeny of apical-basolateral epithelial cell polarity was studied by a comparison of embryonic ureteric bud (UB) and mature cortical collecting duct (CCD) primary cultures. Patch-clamp techniques were applied to identify apical ion channels and to measure specific conductance (in nS/10 pF) of the apical membrane (ga) and of the whole cell (Gw). In UB, Gw (1.3 +/- 0.17; n = 32) and ga (1.4 +/- 0.15; n = 9) were not different, whereas they differed greatly in CCD (Gw: 0.79 +/- 0.07, n = 35; ga: 2.3 +/- 0.38, n = 9). In UB, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) (100 microM) similarly reduced ga and Gw by 0.66 +/- 0.21 (n = 9) and 0.48 +/- 0.07 (n = 7), respectively, whereas DIDS had no effect in CCD. Amiloride (1 mM) did not alter UB conductance, whereas, in CCD, ga was more reduced than Gw (0.75 +/- 0.18, n = 8, vs. 0.22 +/- 0.10, n = 7). In addition to this Na(+)-selective conductance, a nonselective cation (NSC) conductance was enriched sixfold in the apical membrane of CCD, possibly due to apical 9 +/- 1-pS (n = 7) NSC channels, whereas UB apical NSC conductance was low. Apical 16 +/- 2-pS (n = 6) K+ channels were identified in CCD but not in UB. The comparison of both developmental states suggests a differentiation of the apical membrane during UB to CCD ontogeny.
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PMID:Ontogeny of apical membrane ion conductances and channel expression in cortical collecting duct cells. 885 33

Amiloride-sensitive, electrogenic Na+ absorption across the distal nephron plays a vital role in regulating extracellular fluid volume and blood pressure. Recently, two amiloride-sensitive, Na(+)-conducting ion channel cDNAs were cloned. One, an epithelial Na(+)-selective channel (ENaC), is responsible for Na+ absorption throughout the distal nephron. The second, a guanosine 3',5'-cyclic monophosphate (cGMP)-inhibitable cation channel, is conductive to Na+ and Ca2+ and contributes to Na+ absorption across the inner medullary collecting duct (IMCD). As a first step toward understanding the segment-specific contributions(s) of cGMP-gated cation channels and ENaC to Na+ and Ca2+ uptake along the nephron, we used in situ reverse transcription-polymerase chain reaction (RT-PCR) hybridization, solution-phase RT-PCR, and Western blot analysis to examine the nephron and cell-specific expression of these channels in mouse kidney cell lines and/or dissected nephron segments. cGMP-gated cation channel mRNA was detected in proximal tubule, medullary thick ascending limb (mTAL), distal convoluted tubule (DCT), cortical collecting duct (CCD), outer medullary collecting duct (OMCD), and IMCD. cGMP-gated cation channel protein was detected in DCT, CCD, and IMCD cell lines. These observations suggest that hormones that modulate intracellular cGMP levels may regulate Na+, and perhaps Ca2+, uptake throughout the nephron. mRNA for alpha-mENaC, a subunit of the mouse ENaC, was detected in mTAL, DCT, CCD, OMCD, and IMCD. Coexpression of alpha-mENaC and cGMP-gated cation channel mRNAs in mTAL, DCT, CCD, OMCD, and IMCD suggests that both channels may contribute to Na+ absorption in these nephron segments.
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PMID:Cell-specific expression of amiloride-sensitive, Na(+)-conducting ion channels in the kidney. 889 38

Amiloride-sensitive whole cell currents have been reported in M-1 mouse cortical collecting duct cells (Korbmacher et al., J. Gen. Physiol. 102: 761-793, 1993). We have confirmed that amiloride inhibits the whole cell currents but not necessarily the measured whole cell currents. Anomalous responses were eliminated by removing external Na+ and/or introducing paraepithelial shunts. The amiloride-sensitive whole cell currents displayed Goldman rectification. The ionic selectivity sequence of the amiloride-sensitive conductance was Li+ > Na+ >> K+. Growth of M-1 cells on permeable supports increased the amiloride-sensitive whole cell permeability, compared with cells grown on plastic. Single amiloride-sensitive channels were observed, which conformed to the highly selective low-conductance amiloride-sensitive class [Na(5)] of epithelial Na+ channels. Hypotonic pretreatment markedly slowed run-down of channel activity. The gating of the M-1 Na+ channel in excised patches was complex. Open- and closed-state dwell-time distributions from patches that display one operative channel were best described with two or more exponential terms each. We conclude that 1) study of M-1 whole cell Na+ currents is facilitated by reducing the transepithelial potential to zero, 2) these M-1 currents reflect the operation of Na(5) channels, and 3) the Na+ channels display complex kinetics, involving > or = 2 open and > or = 2 closed states.
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PMID:Whole cell and unitary amiloride-sensitive sodium currents in M-1 mouse cortical collecting duct cells. 892 56

Stretching the renal pelvic wall increases ipsilateral afferent renal nerve activity (ARNA). This response is enhanced by inhibiting Na+-K+-ATPase with ouabain, suggesting a modulatory role for intracellular Na+ in the activation of mechanosensitive neurons. The messenger RNA for alpha-, beta-, and gamma-subunits of epithelial Na+ channels (ENaC) is found in collecting duct cells. Because ENaC subunits show homology with genes involved in mechanosensation, we examined whether ENaC mRNA could be found in the pelvic wall and whether the ARNA response to increased renal pelvic pressure was modulated by blockers of the Na+ channel. alpha-, beta-, and gamma-subunits are present in the pelvis. The messenger RNA for the beta- and gamma-subunits is readily detected by in situ hybridization throughout the uroepithelium. The ARNA response to increased renal pelvic pressure was reduced by 53 +/- 10% and 40 +/- 10% (P < 0.01) by renal pelvic perfusion with the inhibitors amiloride and benzamil, respectively. Amiloride inhibited the ouabain-induced enhancement of the ARNA response to increased renal pelvic pressure. The magnitude of this inhibition was inversely correlated with the magnitude of the amiloride-mediated blockade of the ARNA response to increased renal pelvic pressure (P < 0.001). Amiloride also reduced the ARNA response to renal pelvic administration of substance P, a mediator of the ARNA response to increased renal pelvic pressure. We conclude that the ENaC complex in the pelvic uroepithelium participates in the activation of renal pelvic mechanosensitive neurons.
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PMID:Amiloride-sensitive Na+ channels in pelvic uroepithelium involved in renal sensory receptor activation. 984 67

Extracellular nucleotides regulate renal transport. A luminal P2Y2 receptor in mouse cortical collecting duct (CCD) principal cells has been demonstrated elsewhere. Herein the effects of adenosine triphosphate (ATP) and uridine triphosphate (UTP) on electrogenic Na+ absorption in perfused CCD of mice kept on a low-NaCl diet were investigated. Simultaneously, transepithelial voltage (V(te)), transepithelial resistance (R(te)), and fura-2 [Ca2+]i fluorescence were measured. Baseline parameters were V(te), -16.5 +/- 1.2 mV; R(te), 80.8 +/- 7.1 Omega cm2; and equivalent short-circuit current (I(sc)), -261.0 +/- 25.1 microA/cm2 (n = 45). Amiloride (10 microM) almost completely inhibited I(sc) to -3.9 +/- 3.8 microA/cm2 (n = 10). Luminal ATP (100 microM) reduced V(te) from -16.5 +/- 2.1 to -12.5 +/- 1.93 and increased R(te) from 113.1 +/- 16.2 to 123.8 +/- 16.7 Omega cm2, which resulted in a 31.7% inhibition of amiloride-sensitive I(sc) (n = 12). Similarly, luminal UTP reversibly reduced V(te) from -22.0 +/- 2.1 to -13.6 +/- 2.1 mV and increased R(te) from 48.4 +/- 5.3 to 59.2 +/- 7.1 Omega cm2, which resulted in 49.1% inhibition of Na+ absorption (n = 6). In parallel, luminal ATP and UTP elevated [Ca2+]i in CCD, increasing the fura-2 ratio by 2.7 +/- 0.7 and 4.0 +/- 1.2, respectively. Basolateral ATP and UTP (100 microM) also inhibited amiloride-sensitive I(sc) by 21.8 (n = 14) and 20.1% (n = 8), respectively. Inhibition of luminal nucleotide-induced [Ca2+]i increase by Ca2+ store depletion with cyclopiazonic acid (3 microM) did not affect nucleotide-mediated inhibition of Na+ transport (n = 7). No evidence indicated the activation of a luminal Ca2+-activated Cl- conductance, a phenomenon previously shown in M-1 CCD cells (J Physiol 524: 77-99, 2000). In essence, these data indicate that luminal ATP and UTP, most likely via P2Y2 receptors, mediate inhibition of amiloride-sensitive I(sc) in perfused mouse CCD. This inhibition appears to occurs independently of an increase of cytosolic Ca2+.
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PMID:Luminal P2Y2 receptor-mediated inhibition of Na+ absorption in isolated perfused mouse CCD. 1175 16

In vitro studies suggest that collecting duct-derived (CD-derived) endothelin-1 (ET-1) can regulate renal Na reabsorption; however, the physiologic role of CD-derived ET-1 is unknown. Consequently, the physiologic effect of selective disruption of the ET-1 gene in the CD of mice was determined. Mice heterozygous for aquaporin2 promoter Cre recombinase and homozygous for loxP-flanked exon 2 of the ET-1 gene (called CD-specific KO of ET-1 [CD ET-1 KO] mice) were generated. These animals had no CD ET-1 mRNA and had reduced urinary ET-1 excretion. CD ET-1 KO mice on a normal Na diet were hypertensive, while body weight, Na excretion, urinary aldosterone excretion, and plasma renin activity were unchanged. CD ET-1 KO mice on a high-Na diet had worsened hypertension, reduced urinary Na excretion, and excessive weight gain, but showed no differences between aldosterone excretion and plasma renin activity. Amiloride or furosemide reduced BP in CD ET-1 KO mice on a normal or high-Na diet and prevented excessive Na retention in salt-loaded CD ET-1 KO mice. These studies indicate that CD-derived ET-1 is an important physiologic regulator of renal Na excretion and systemic BP.
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PMID:Collecting duct-specific knockout of endothelin-1 causes hypertension and sodium retention. 1531 87

Amiloride-sensitive sodium entry, via the epithelial sodium channel (ENaC), is the rate-limiting step for Na+ absorption in kidney collecting ducts, and epidermal growth factor (EGF) inhibits Na+ transport and ENaC expression. A pathognomonic feature of polycystic kidney disease (PKD) is EGF receptor mislocalization to the apical plasma membrane and EGF/EGF receptor axis overactivity. Immunohistochemical and biochemical analysis revealed mislocalization of EGF receptor and excessive activation of the p42/44 extracellular signal-regulated protein kinase pathway (ERK1/2) in kidneys from cystic mice compared with noncystic littermates. Primary monolayer cultures of noncystic and cystic murine collecting duct principal cells were used to identify aberrant EGF-dependent ERK1/2 activation and regulation of Na+ transport associated with autosomal recessive PKD. Addition of EGF to the basolateral bathing solution of noncystic or cystic monolayers led to p42/44 phosphorylation and inhibition of Na+ transport (30-35%), whereas apical EGF was effective only in monolayers derived from cystic mice. p42/44 Phosphorylation and inhibition of Na+ transport were prevented by prior treatment of the cells with an ERK kinase inhibitor. Chronic treatment (24 h) of noncystic and cystic monolayers with basolateral EGF elicited sustained inhibition of Na+ absorption (50-55%) and a reduction in steady-state ENaC mRNA levels (50-75%). In contrast, addition of EGF to the apical bathing solution (24 h) had no effect in noncystic monolayers but led to inhibition of Na+ transport (50-60%) and decreased ENaC expression (45-60%) in cystic cells. Pretreatment of the monolayers with an ERK kinase inhibitor abolished the chronic effects of EGF on Na+ transport. The results of these studies reveal that the mislocalized apical EGF receptors are functionally coupled to the ERK pathway and that abnormal EGF-dependent regulation of ENaC function and expression may contribute to PKD pathophysiology.
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PMID:Abnormal EGF-dependent regulation of sodium absorption in ARPKD collecting duct cells. 1552 85

The Tg737 degrees (rpk) autosomal recessive polycystic kidney disease (ARPKD) mouse carries a hypomorphic mutation in the Tg737 gene. Because of the absence of its protein product Polaris, the nonmotile primary monocilium central to the luminal membrane of ductal epithelia, such as the cortical collecting duct (CCD) principal cell (PC), is malformed. Although the functions of the renal monocilium remain elusive, primary monocilia or flagella on neurons act as sensory organelles. Thus we hypothesized that the PC monocilium functions as a cellular sensor. To test this hypothesis, we assessed the contribution of Polaris and cilium structure and function to renal epithelial ion transport electrophysiology. Properties of Tg737 degrees (rpk) mutant CCD PC clones were compared with clones genetically rescued with wild-type Tg737 cDNA. All cells were grown as polarized cell monolayers with similarly high transepithelial resistance on permeable filter supports. Three- to fourfold elevated transepithelial voltage (V(te)) and short-circuit current (I(sc)) were measured in mutant orpk monolayers vs. rescued controls. Pharmacological and cell biological examination of this enhanced electrical end point in mutant monolayers revealed that epithelial Na(+) channels (ENaCs) were upregulated. Amiloride, ENaC-selective amiloride analogs (benzamil and phenamil), and protease inhibitors (aprotinin and leupeptin) attenuated heightened V(te) and I(sc). Higher concentrations of additional amiloride analogs (ethylisopropylamiloride and dimethylamiloride) also revealed inhibition of V(te). Cell culture requirements and manipulations were also consistent with heightened ENaC expression and function. Together, these data suggest that ENaC expression and/or function are upregulated in the luminal membrane of mutant, cilium-deficient orpk CCD PC monolayers vs. cilium-competent controls. When the genetic lesion causes loss or malformation of the monocilium, ENaC-driven Na(+) hyperabsorption may explain the rapid emergence of severe hypertension in a majority of patients with ARPKD.
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PMID:Heightened epithelial Na+ channel-mediated Na+ absorption in a murine polycystic kidney disease model epithelium lacking apical monocilia. 1653 71


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