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)

Dehydration increased the expression of aquaporin of collecting duct (AQP-2) and translocated AQP-2 to the apical plasma membranes from cytoplasmic vesicles of collecting duct cells. We determined whether the abrupt decrease in circulating arginine vasopressin (AVP) by giving excess water affects the expression of AQP-2 mRNA and subcellular localization of AQP-2 in collecting duct cells of the dehydrated rats. The 72-h water deprivation increased plasma AVP levels to 3.1 pg/ml and the expression of AQP-2 mRNA by 336% in rats, which were concomitantly abolished by the 40 ml/kg oral water load. A 50% inhibition ofAQP-2 mRNA expression was obtained with 20 min after the forced water load. In immunohistochemistry and electron microscopy, the AQP-2 was manifestly present around the apical edge of collecting duct cells in the 72-h dehydrated rats. The AQP-2 was diffusely translocated into the cytoplasm 1 h after the forced water administration. These results indicate that AVP plays the on-off regulation of AQP-2 mRNA expression and that a majority of AQP-2 is regulated by the shuttle recycling in the collecting duct cells.
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PMID:Alteration in water channel AQP-2 by removal of AVP stimulation in collecting duct cells of dehydrated rats. 912 94

The mRNA expression and localization of the aquaporin (AQP) family in rat kidney were examined by ribonuclease protection assay and immunohistochemistry. AQP1, AQP2, AQP3, and AQP4 mRNA were hardly detectable in 16-day gestation fetuses. AQP1 mRNA was explosively expressed at 1 wk, keeping the level throughout life. AQP2 mRNA expression was apparently noticed in 18-day fetuses and was enhanced gradually with age to reach a plateau at 4 wk. AQP3 and AQP4 mRNA expression was significantly found at birth but was not changed remarkably thereafter. AQP2 protein appeared first at the apical side of collecting duct cells in 18-day fetuses. The staining intensity at the site increased with age, and basolateral staining was added in adult rats. AQP3 was distinctly demonstrated at the basolateral side of collecting duct cells after birth, and the staining intensity was almost stable throughout life. The progressive induction of AQP2 expression in the first 4 wk after birth is presumed to contribute to the maturation of urinary concentrating capacity during the kidney development.
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PMID:Expression of AQP family in rat kidneys during development and maturation. 912 96

Vasopressin plays an essential role for the regulation of water balance by activating the collecting duct-specific water channel, aquaporin-2 (AQP2). Here we present evidence that vasopressin may also act as a long-term, transcriptional regulator of AQP2. The studies were performed on LLC-PK1 cells, which normally express V2 receptor (V2R) and which were transfected with a fragment of the human AQP2 promoter. Activation of the adenylate cyclase-coupled V2R in LLC-PK1 cells induced phosphorylation of adenosine 3',5'-cyclic monophosphate (cAMP) responsive element binding protein (CREB) and expression of c-Fos. Binding of these factors to the CRE and AP1 site did, in combination, lead to AQP2 promoter activation. These results establish the role of vasopressin as a regulator of transcription and are the first example of how a message from a highly specific receptor is, via a dual effect of the cAMP signal on CREB and immediate early gene expression, transduced to the transcription of a final target protein with known biological effects.
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PMID:Adenylate cyclase-coupled vasopressin receptor activates AQP2 promoter via a dual effect on CRE and AP1 elements. 914 44

We tested whether severe congestive heart failure (CHF), a condition associated with excess free-water retention, is accompanied by altered regulation of the vasopressin-regulated water channel, aquaporin-2 (AQP2), in the renal collecting duct. CHF was induced by left coronary artery ligation. Compared with sham-operated animals, rats with CHF had severe heart failure with elevated left ventricular end-diastolic pressures (LVEDP): 26.9 +/- 3.4 vs. 4.1 +/- 0.3 mmHg, and reduced plasma sodium concentrations (142.2 +/- 1. 6 vs. 149.1 +/- 1.1 mEq/liter). Quantitative immunoblotting of total kidney membrane fractions revealed a significant increase in AQP2 expression in animals with CHF (267 +/- 53%, n = 12) relative to sham-operated controls (100 +/- 13%, n = 14). In contrast, immunoblotting demonstrated a lack of an increase in expression of AQP1 and AQP3 water channel expression, indicating that the effect on AQP2 was selective. Furthermore, postinfarction animals without LVEDP elevation or plasma Na reduction showed no increase in AQP2 expression (121 +/- 28% of sham levels, n = 6). Immunocytochemistry and immunoelectron microscopy demonstrated very abundant labeling of the apical plasma membrane and relatively little labeling of intracellular vesicles in collecting duct cells from rats with severe CHF, consistent with enhanced trafficking of AQP2 to the apical plasma membrane. The selective increase in AQP2 expression and enhanced plasma membrane targeting provide an explanation for the development of water retention and hyponatremia in severe CHF.
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PMID:Congestive heart failure in rats is associated with increased expression and targeting of aquaporin-2 water channel in collecting duct. 914 58

Like mammalian kidney collecting duct, the water permeability of frog urinary bladder epithelial cells is antidiuretic hormone (ADH)-sensitive. In kidney, this permeability is mediated by water channels named aquaporins. We recently reported the cloning of the frog aquaporin CHIP (FA-CHIP), a water channel from frog urinary bladder. FA-CHIP has 79% identity with rat Aquaporin 1 (AQP1) and only 42% identity with the kidney collecting duct Aquaporin 2 (AQP2). The purpose of this study was to examine the localization of FA-CHIP in frog urinary bladder. We raised antibodies against peptides of 15 to 17 residues, encompassing the N-ter and C-ter regions of FA-CHIP. Anti-FA-CHIP antibodies were used for Western blotting, indirect immunofluorescence microscopy and gold labeling electron microscopy in urinary bladder and other frog tissues. By Western blotting of frog urinary bladder total homogenate, the antibodies recognized a band of 29 kDa and glycosylated forms of the protein between 40 and 70 kDa. No signal was found on membrane preparations from epithelial cell homogenate. FA-CHIP was also found in frog skin, brain, gall bladder, and lung. In immunofluorescence microscopy on urinary bladder sections, FA-CHIP was localized to endothelial cells of blood capillaries and on mesothelial cells of the serosal face. Red blood cells, epithelial and basal cells were unstained. The localization of FA-CHIP in cell plasma membranes was confirmed by gold labeling electron microscopy. In other positive tissues, FA-CHIP was also localized to capillaries. In brain, plasma membranes of epithelial cells were also stained. In conclusion, like its mammalian homologue AQP1, FA-CHIP appears to be localized to constitutively water permeable cells of frog. Therefore, it belongs to the AQP1 family of proteins although unlike AQP1, FA-CHIP is absent from red blood cells and kidney. In frog urinary bladder and skin, FA-CHIP probably plays an important role in water transport across the barriers in series with the ADH-sensitive epithelial cells.
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PMID:Localization of the FA-CHIP water channel in frog urinary bladder. 924 82

Vasopressin regulates water excretion from the kidney by increasing the osmotic water permeability of the renal collecting duct. The aquaporin-2 water channel has been demonstrated to be the target for this action of vasopressin. Recent studies have demonstrated that vasopressin, acting through cyclic AMP, triggers fusion of aquaporin-2-bearing vesicles with the apical plasma membrane of the collecting duct principal cells. The vesicle-targeting proteins synaptobrevin-2 and syntaxin-4 are proposed to play roles in this process.
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PMID:Regulation of aquaporin-2 water channel trafficking by vasopressin. 926 Oct 56

The aquaporins are a recently recognized family of water channels that mediate water transport in kidney and in other organs. Aquaporin-2, 'vasopressin-regulated water channel', is regulated by vasopressin in two ways to account for overall control of collecting duct water permeability. First, vasopressin has a short-term effect in triggering translocation of aquaporin-2-containing intracytoplasmic vesicles to the apical plasma membrane, thus increasing principal cell water permeability. Second, vasopressin has a long-term effect in increasing the abundance of aquaporin-2 in collecting duct principal cells, increasing the maximal attainable water permeability. Using animal models, defects in these control mechanisms have been shown to be associated with several disorders of water balance, including central diabetes insipidus, congenital nephrogenic diabetes insipidus, acquired diabetes insipidus, syndrome of inappropriate antidiuretic hormone secretion, and several extracellular fluid volume expanded states.
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PMID:Role of aquaporins in water balance disorders. 926 86

In bilateral ureteral obstruction, both aquaporin-2 (AQP2) levels and urinary concentrating capacity are markedly reduced. However, the mechanisms involved in AQP2 downregulation are unknown. In rats with unilateral ureteral obstruction (UUO) the relative role of intrarenal and systemic factors can be evaluated. Semiquantitative immunoblotting revealed a marked decrease in AQP2 in obstructed kidneys to 23 +/- 7% (n = 9) of sham levels. This downregulation persisted 24 h after release of UUO. Furthermore, there was a significant but less extensive downregulation of AQP2 in the nonobstructed kidneys to 75 +/- 7% (n = 9) of sham levels. Consistent with impairment of collecting duct water reabsorption, free water clearance was greatly elevated in the obstructed kidneys (-2 +/- 1 microliter-min-1.kg-1, determined immediately after release) and only moderately elevated in nonobstructed kidneys (-44 +/- 5 microliters.min-1.kg-1) compared with sham-operated controls (-59 +/- 3 microliters.min-1.kg-1). Also AQP2 mRNA levels were reduced in obstructed kidneys. Immunocytochemistry confirmed the marked decrease in AQP2 expression in obstructed kidneys. In nonobstructed kidneys AQP2 was predominantly found in intracellular vesicles, which together with the reduced expression and elevated free water clearance strongly suggests a role of AQP2 in the observed compensatory diuresis from nonobstructed kidneys. The much lower AQP2 protein and mRNA levels in obstructed vs. nonobstructed kidneys are consistent with intrarenal factors playing a major role for downregulation of AQP2.
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PMID:Downregulation of aquaporin-2 parallels changes in renal water excretion in unilateral ureteral obstruction. 927 82

Water transport across the mammalian collecting tubule is regulated by vasopressin-dependent aquaporin-2 insertion into and retrieval from the apical cell membrane. To establish a cell line that properly expresses aquaporin-2 and its hormone-dependent shuttling, Madin-Darby canine kidney cells were stably transfected with an aquaporin-2 expression construct. Cells of a representative clone (wild-type 10 [WT-10]) were grown on semipermeable supports, and transcellular osmotic water permeability (Pf; in microm/s +/- SEM) was measured. The basal Pf of WT-10 cells, which was lowered with indomethacin, increased from 10.6 +/- 0.8 to 35.7 +/- 1.2 upon incubation with 1-desamino-8-D-arginine vasopressin (dDAVP). This increase coincided with the translocation of aquaporin-2 from an intracellular compartment to the apical membrane. The Pf of untransfected cells (6.5 +/- 0.8) was unchanged by dDAVP. Kinetic studies with WT-10 cells revealed that maximal Pf was obtained within 30 min after dDAVP addition, which remained elevated for at least 90 min. Intracellular cAMP levels peaked within 5 min after dDAVP admission and decreased to basal levels within 45 min. After preincubation with dDAVP, the Pf decreased within 15 min after dDAVP washout and returned to basal levels within 75 min. In conclusion, the WT-10 cells mimic the vasopressin-regulated transcellular water transport and aquaporin-2 translocation as found in collecting duct cells to a great extent, and therefore constitute an in vitro cell model that can be used to study the regulation of transcellular water transport in detail and provide a simplified test system for screening putative aquaporin-2 blockers.
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PMID:Aquaporin-2 transfection of Madin-Darby canine kidney cells reconstitutes vasopressin-regulated transcellular osmotic water transport. 933 76

Previously, we demonstrated that a putative vesicle-targeting protein, syntaxin-4, is expressed in renal collecting duct principal cells and is localized to the apical plasma membrane, suggesting a role in targeting aquaporin-2-containing vesicles to the apical plasma membrane. To investigate whether other syntaxin isoforms are present in the renal collecting duct, we determined the intrarenal localization of syntaxin-2 and -3. Reverse transcription-polymerase chain reaction (RT-PCR) experiments using total RNA extracted from kidney and various organs revealed that both syntaxin-2 and -3 are expressed in kidney cortex and medulla. RT-PCR experiments using microdissected tubules and vascular structures from the kidney revealed that syntaxin-3 mRNA, but not syntaxin-2, is expressed in collecting duct cells. Syntaxin-3 mRNA was also relatively abundant in the thick ascending limb of Henle's loop and in vasa recta. Syntaxin-2 mRNA was found chiefly in glomeruli. To investigate the localization of syntaxin-3 protein, a peptide-derived polyclonal antibody was raised in rabbits. In immunoblotting experiments, this antibody labeled a 37-kDa protein in inner medulla that was most abundant in plasma membrane-enriched subcellular fractions. Immunoperoxidase labeling of thin cryosections combined with immunogold electron microscopy showed that, in contrast to the labeling seen for syntaxin-4, syntaxin-3 labeling in medullary collecting duct was predominantly in the basolateral plasma membrane of intercalated cells. These results suggest the possibility that syntaxin-3 may be involved in selective targeting of acid-base transporters and/or in basolateral membrane remodeling in response to systemic acid-base perturbations.
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PMID:Expression of syntaxins in rat kidney. 937 35


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