UNIPROT:P41181 - FACTA Search

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Query: UNIPROT:P41181 (collecting duct)
5,183 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is well established that the terminal renal collecting duct is capable of electrogenic Na+ absorption. The present experiments examined other active ion transport processes in primary cultures of the rat inner medullary collecting duct. When the amiloride analogue benzamil inhibited electrogenic Na+ absorption, cAMP agonists stimulated a transmonolayer short circuit current that was not dependent on the presence of Na+ in the apical solution, but was dependent on the presence of Cl- and HCO3-. This current was not inhibited by the loop diuretic bumetanide, but was inhibited by ouabain, an inhibitor of the Na+/K+ pump. The current was reduced by anion transport inhibitors, with a profile similar to that seen for inhibitors of the cystic fibrosis transmembrane conductance regulator (CFATR) Cl- channel. Using several PCR strategies, we demonstrated fragments of the predicted lengths and sequence identity with the rat CFTR. Using whole-cell patch-clamp analysis, we demonstrated a cAMP-stimulated Cl- current with characteristics of the CFTR. We conclude that the rat inner medullary collecting duct has the capacity to secrete anions. It is highly likely that the CFTR Cl- channel is involved in this process.
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PMID:Anion secretion by the inner medullary collecting duct. Evidence for involvement of the cystic fibrosis transmembrane conductance regulator. 753 87

Previously we demonstrated that the inner medullary collecting duct cell line mIMCD-K2 secretes Cl- by an electrogenic mechanism [N. L. Kizer, B. Lewis, and B. A. Stanton. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F347-F355, 1995; N. L. Kizer, D. Vandorpe, B. Lewis, B. Bunting, J. Russell, and B. A. Stanton. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F854-F861, 1995]. The goal of the present study was to characterize the Cl- channel responsible for adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated Cl- secretion. To this end, using the patch-clamp technique, we measured Cl- currents. In whole cell patch-clamp experiments, 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP) activated Cl- currents that were time and voltage independent, inhibited by diphenylamine 2-carboxylate (DPC), and had a linear current-voltage (I-V) relation. In cell-attached patches of the apical membrane, we identified 7-pS Cl- channels that were stimulated by CPT-cAMP. In inside-out patches with Cl- in the pipette and bath solutions, Cl- currents had a linear I-V relation. The halide permeability sequence was PCl = PBr > PI. The Cl- channel inhibitors DPC, 5-nitro-2-(3-phenylpropylamino)-benzoic acid, and glibenclamide blocked the 7-pS Cl- channel, whereas 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid was ineffective. By reverse transcriptase polymerase chain reaction, we isolated a partial cDNA clone encoding the cystic fibrosis transmembrane conductance regulator in mIMCD-K2 cells. We conclude that cAMP stimulates electrogenic Cl- secretion in inner medullary collecting duct cells by activating cystic fibrosis transmembrane conductance regulator Cl- channels.
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PMID:CFTR mediates electrogenic chloride secretion in mouse inner medullary collecting duct (mIMCD-K2) cells. 757 98

Previously, we demonstrated that the mIMCD-K2 cell line, derived from the inner medullary collecting duct (IMCD) of a transgenic mouse, secretes Cl- by an electrogenic mechanism [N. L. Kizer, B. Lewis, and B. A. Stanton, Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F347-F355, 1995]. The objective of the present study was to characterize the cellular mechanisms of electrogenic Cl- secretion (IscCl) and to determine whether arginine vasopressin (AVP) and adenosine 3',5'-cyclic monophosphate (cAMP) stimulate IscCl. To this end, we measured IscCl across monolayers of mIMCD-K2 cells mounted in Ussing-type chambers. AVP increased IscCl with a Michaelis constant (Km) of 2.1 +/- 0.7 x 10(-12) M. 1-Desamino-8-D-AVP, a specific V2 receptor agonist, increased IscCl from 3.3 +/- 0.4 to 17.4 +/- 1.3 microA/cm2, 8-(4-Chlorophenylthio)-cAMP, a cell-permanent analogue of cAMP, a second messenger of AVP, increased IscCl from 1.4 +/- 0.3 to 15.2 +/- 1.2 microA/cm2. Furosemide and bumetanide, inhibitors of Na(+)-2Cl(-)-K+ cotransport, and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), an inhibitor of Cl-/HCO3- exchange, reduced IscCl when added to the basolateral solution. Our data suggest that AVP, via V2 receptors, and the second messenger cAMP stimulate IscCl and that Cl- secretion by mIMCD-K2 cells involves uptake of Cl- across the basolateral membrane by Na(+)-2Cl(-)-K+ cotransport and Cl-/HCO3- exchange and diffusion out of the cells across the apical membrane by cystic fibrosis transmembrane conductance regulator Cl- channels.
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PMID:Vasopressin and cAMP stimulate electrogenic chloride secretion in an IMCD cell line. 777 14

Previously, we demonstrated that a mouse inner medullary collecting duct cell line (mIMCD-K2) secretes Cl- by an electrogenic mechanism via cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channels [N. L. Kizer, B. Lewis, and B. A. Stanton. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F347-F355, 1995; N. L. Kizer, D. Vandorpe, B. Lewis, B. Bunting, J. Russell, and B. A. Stanton. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F854-F861, 1995; D. Vandorpe, N. Kizer, F. Ciampolillo-Bates, B. Moyer, K. Karlson, W. B. Guggino, and B. A. Stanton. Am. J. Physiol. 269 (Cell Physiol. 38): C683-C689, 1995]. The objective of the present study was to determine whether adenosine, and adenosine A1 receptors (A1AR) specifically, regulate electrogenic Cl- secretion (IscCl) in mIMCD-K2 cells. Neither N6-cyclohexyladenosine (CHA), a specific A1AR agonist, nor 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a specific A1AR antagonist, altered basal, unstimulated IscCl in monolayers of mIMCD-K2 cells mounted in Ussing-type chambers. In contrast, DPCPX increased arginine vasopressin (AVP)-stimulated IscCl, an effect that was reversed by CHA. Adenosine deaminase (ADA), which oxidatively deaminates adenosine to inosine, increased AVP-stimulated IscCl. CHA reversed the stimulatory effect of ADA on AVP-stimulated IscCl. These results suggest that adenosine, via A1AR, inhibits AVP-stimulated IscCl. To identify the source(s) of extracellular adenosine, we examined the effects of dipyridamole, an inhibitor of nucleoside transport, and alpha,beta-methyleneadenosine 5'-diphosphate (AOPCP), an inhibitor of ecto-5'-nucleotidase, on AVP-stimulated IscCl. Both compounds increased AVP-stimulated IscCl. CHA reversed the stimulatory effect of dipyridamole and AOPCP on IscCl. Neither ADA nor CHA had an effect on 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (CPT-cAMP)-stimulated IscCl. Moreover, U-73122, an inhibitor of phospholipase C, failed to attenuate the increase in AVP-stimulated IscCl elicited by dipyridamole and AOPCP or the decrease in AVP-stimulated IscCl elicited by CHA. We conclude that adenosine, released by a nucleoside transporter and formed extracellularly by the breakdown of AMP, binds to A1AR, and decreases AVP-stimulated IscCl in mIMCD-K2 cells by reducing intracellular cAMP levels.
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PMID:Adenosine inhibits arginine vasopressin-stimulated chloride secretion in a mouse IMCD cell line (mIMCD-K2). 859 84

The rat inner medullary collecting duct is capable of secreting anions. We previously showed that adenosine 3',5'-cyclic monophosphate (cAMP) stimulates anion secretion; the apical membrane anion exit pathway activated by cAMP appears to be the cystic fibrosis transmembrane conductance regulator Cl- channel. The present experiments were designed to test the hypothesis that the entry pathway across the basolateral membrane is a Cl-/HCO3- exchanger operating in parallel with an Na+/H+ exchanger. We investigated the mechanism by measuring cell Cl-, cell pH, and short-circuit current under a variety of conditions designed to uncover these pathways. cAMP agonists caused little change in cell Cl-, but they produced a consistent intracellular acidification. This acidification was dependent on HCO3-, but not on Cl-, and was not inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). The presence of the basolateral Cl-/HCO3- exchanger was demonstrated by several maneuvers, and its activity was inhibited by DIDS. Applied to the basolateral solution, DIDS did not inhibit the cAMP-dependent anion current but actually stimulated it. We conclude that cAMP-stimulated anion secretion does not require activation of the basolateral Cl-/HCO3- exchanger. The transporter responsible for Cl- entry across the basolateral membrane remains unknown and is not inhibited by a variety of anion transport inhibitors, including DIDS, bumetanide, and hydrochlorothiazide. The cell acidification induced by cAMP appears to be independent of acid secretion and is the result of activation of one or more HCO3- exit pathways that are resistant to DIDS but are inhibited by a nonspecific anion transport inhibitor, 5-nitro-2-(3-phenylpro-pylamino) benzoic acid. We present a revised model for anion transport by the rat inner medullary collecting duct.
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PMID:Effect of cAMP agonists on cell pH and anion transport by cultured rat inner medullary collecting duct cells. 876 31

The cystic fibrosis transmembrane conductance regulator (CFTR) is a adenosine 3',5'-cyclic monophosphate-activated chloride channel located in the apical membrane of many epithelial cells, and it may play a significant role in the kidney. Recent functional evidence from our laboratory suggests that CFTR may be expressed by the cortical collecting duct (CCD). Therefore, in the present study, the reverse transcription-polymerase chain reaction (RT-PCR) technique was utilized to detect CFTR mRNA in the M-1 mouse CCD cell line and in immunoselected rabbit CCD cells. Primers were constructed to amplify the cDNA sequence encoding the first nucleotide binding domain of CFTR. CFTR PCR products were obtained from both M-1 and rabbit CCD cDNA preparations. The identify of the product amplified from M-1 cell cDNA was confirmed by restriction digestion analysis. The rabbit CCD PCR product was sequenced, and its deduced amino acid sequence was found to be 97% homologous to the corresponding regions of human CFTR. The level of CFTR cDNA detected after 30 cycles of amplification of CCD cDNA was only 49 +/- 8 (n = 9) times lower than the level of beta-actin PCR product obtained from the same sample, suggesting that the levels of CFTR mRNA present in the CCD are physiologically relevant. Northern analysis, using a cRNA probe corresponding to the amplified region on the mRNA from CCD cells, revealed a single hybridizing species with a size of approximately 6.5 kb. Finally, CFTR PCR was performed with cDNA preparations originating from principal cells (PC), beta-intercalated cells (beta-ICC), and alpha-ICC obtained by fluorescence-activated cell sorting of rabbit CCD. CFTR PCR products were obtained from all three cell types, with the most abundant levels found in beta-ICC. beta-ICC expressed 25-fold (n = 4, P < 0.001) and 4.5-fold (n = 7, P < 0.001) higher levels than PC and alpha-ICC, respectively. This distribution pattern suggests that, within the CCD, CFTR plays a role primarily in beta-ICC function.
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PMID:CFTR expression in cortical collecting duct cells. 876 45

Confluent M-1 mouse cortical collecting duct (CCD) cells express highly selective low-conductance amiloride-sensitive Na+ channels (B. Letz, A. Ackermann, C. M. Canessa, B. C. Rossier, and C. Korbmacher, J. Membr. Biol. 148: 129-143, 1995). Here we investigated the effect of forskolin on membrane voltage and whole cell currents of confluent M-1 cells using the patch-clamp technique. Forskolin (1 microM) reduced the hyperpolarization in response to amiloride (10 microM) from 17 to 4 mV and decreased the amiloride-sensitive Na+ inward currents from 81 to 26 pA. Furthermore, forskolin increased the hyperpolarization caused by changing from an apical low-Cl- solution (9 mM) to a high-Cl- solution (149 mM) from 11 to 30 mV and increased the magnitude of the inward current changes induced by alternating between high-Cl- and low-Cl- solutions from 25 to 138 pA. This demonstrates that forskolin stimulates an apical Cl- conductance. Anion substitution experiments revealed a permeability sequence SCN- > Br- > Cl- > I- >> gluconate. This suggests that the stimulated channels are cystic fibrosis transmembrane conductance regulator (CFTR)-like Cl- channels. 3-Isobutyl-1-methylxanthine and 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate mimicked the effects of forskolin, whereas 1,9-dideoxyforskolin had no effect. We conclude that, in addition to amiloride-sensitive Na+ channels, CFTR-like Cl- channels are present in the apical membrane of confluent M-1 cells. An increase in intracellular adenosine 3',5'-cyclic monophosphate (cAMP) activates these Cl- channels and concurrently reduces the activity of the Na+ channels. This reciprocal regulation by cAMP suggests that the channels are functionally coupled.
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PMID:cAMP stimulates CFTR-like Cl- channels and inhibits amiloride-sensitive Na+ channels in mouse CCD cells. 912 10

The cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel is expressed in all nephron segments. Although mutations in CFTR are not associated with major changes in renal function, drug excretion by the kidneys is altered in cystic fibrosis (CF) as is the ability of the kidneys to concentrate and dilute the urine and excrete a salt load. It is not clear if these changes in renal function are secondary to decreased extracellular fluid volume caused by excessive losses of NaCl in sweat and feces or if they are related to primary defects in renal function caused by mutations in CFTR. Considerable evidence supports a role for CFTR in mediating Cl- secretion by the distal tubule, principal cells in the cortical collecting duct (CCD) and the inner medullary collecting duct (IMCD). In addition, CFTR is responsible for Cl- secretion into the lumen of cysts in polycystic kidneys and, therefore, contributes to cyst enlargement. Under some conditions--when Na+ absorption across the apical membrane of principal cells in the CCD is stimulated and the apical membrane potential is depolarized--the electrochemical gradient for Cl- will support Cl- absorption via CFTR Cl- channels. In addition to its function as a 3',5'-cAMP-activated Cl- channel, CFTR may play a role in intracellular vesicle acidification, protein processing, protein trafficking, secretion of ATP and the regulation of the epithelial Na channel (ENaC) and the secretory K+ channel (ROMK2) which mediate Na+ and K+ transport, respectively, across the CCD. Thus, CFTR may regulate Na+ and K+ excretion by the kidneys. The most common mutation in CFTR is delta F508, a mutation which causes improper folding of CFTR such that it is retained within the endoplasmic reticulum where it is degraded. Thus, in the majority of cases, CF is a trafficking disease. However, nothing is known about the intracellular trafficking of CFTR in the kidney. In preliminary studies we have developed a living cell model to study the intracellular trafficking of CFTR and delta F508-CFTR in renal epithelial cells in real time. Our ultimate goal is to elucidate the intracellular trafficking of CFTR and to identify therapeutic approaches to restore normal function to renal cells in CF and to block CFTR-mediated Cl- secretion in cysts in polycystic kidneys.
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PMID:Cystic fibrosis transmembrane conductance regulator (CFTR) and renal function. 926 86

The effects of aldosterone and vasopressin on Cl- transport were investigated in a mouse cortical collecting duct (mpkCCD) cell line derived from a transgenic mouse carrying the SV40 large T antigen driven by the proximal regulatory sequences of the L-pyruvate kinase gene. The cells had features of a tight epithelium and expressed the amiloride-sensitive sodium channel and the cystic fibrosis transmembrane conductance regulator (CFTR) genes. dD-arginine vasopressin (dDAVP) caused a rapid, dose-dependent, increase in short-circuit current (Isc). Experiments with ion channel blockers and apical ion substitution showed that the current represented amiloride-sensitive Na+ and 5-nitro-2-(3-phenylpropylamino)benzoate-sensitive and glibenclamide-sensitive Cl- fluxes. Aldosterone (5 x 10(-7)M for 3 or 24 hr) stimulated Isc and apical-to-basal 22Na+ flux by 3-fold. 36Cl- flux studies showed that dDAVP and aldosterone stimulated net Cl- reabsorption and that dDAVP potentiated the action of aldosterone on Cl- transport. Whereas aldosterone affected only the apical-to-basal 36Cl- flux, dDAVP mainly increased the apical-to-basal Cl- flux and the basal-to-apical flux of Cl- to a lesser extent. These results suggest that the discrete dDAVP-elicited Cl- secretion involves the CFTR and that dDAVP and aldosterone may affect in different ways the observed increased Cl- reabsorption in this model of mouse cultured cortical collecting duct cells.
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PMID:Differential effects of aldosterone and vasopressin on chloride fluxes in transimmortalized mouse cortical collecting duct cells. 963 46

In autosomal dominant polycystic kidney disease (ADPKD), the genetic defect results in the slow growth of a multitude of epithelial cysts within the renal parenchyma. Cysts originate within the glomeruli and all tubular structures, and their growth is the result of proliferation of incompletely differentiated epithelial cells and the accumulation of fluid within the cysts. The majority of cysts disconnect from tubular structures as they grow but still accumulate fluid within the lumen. The fluid accumulation is the result of secretion of fluid driven by active transepithelial Cl- secretion. Proliferation of the cells and fluid secretion are activated by agonists of the cAMP signaling pathway. The transport mechanisms involved include the cystic fibrosis transmembrane conductance regulator (CFTR) present in the apical membrane of the cystic cells and a bumetanide-sensitive transporter located in the basolateral membrane. A lipid factor, called cyst activating factor, has been found in the cystic fluid. Cyst activating factor stimulates cAMP production, proliferation, and fluid secretion by cultured renal epithelial cells and also is a chemotactic agent. Cysts also appear in the intrahepatic biliary tree in ADPKD. Normal ductal cells secrete Cl- and HCO3-. The cystic ductal cell also secretes Cl-, but HCO3- secretion is diminished, probably as the result of a lower population of Cl-/HCO3- exchangers in the apical membrane as compared with the normal cells. Some segments of the normal renal tubule are also capable of utilizing CFTR to secrete Cl-, particularly the inner medullary collecting duct. The ability of Madin-Darby canine kidney cells and normal human kidney cortex cells to form cysts in culture and to secrete fluid and the functional similarities between these incompletely differentiated, proliferative cells and developing cells in the intestinal crypt and in the fetal lung have led us to suggest that Cl- and fluid secretion may be a common property of at least some renal epithelial cells in an intermediate stage of development. The genetic defect in ADPKD may not directly affect membrane transport mechanisms but rather may arrest the development of certain renal epithelial cells in an incompletely differentiated, proliferative stage.
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PMID:Epithelial transport in polycystic kidney disease. 979 May 73

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