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)

The purpose of these studies was to characterize the development of H+ secretion by cultured inner medullary collecting duct (IMCD) cells. Differentiated IMCD cells derived from rat papillae develop in culture N-ethylmaleimide (NEM)- and dicyclohexylcarbodiimide (DCCD)-sensitive Na+-independent H+ pump, but showed substantial heterogeneity. Cells with pHi greater than or equal to 7.1, measured by 2',7'-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF), showed more H+ pumping than did those with pHi less than 7.1. Quiescent cells in domes and in the center of growing nests often showed active H+ pumping activity, but rarely exhibited Na+-H+ exchange, whereas dividing cells at the periphery of the nests showed only Na+-H+ exchange. Differentiated IMCD cells also showed Na+-independent 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS)-sensitive Cl(-)-HCO3- exchange that functioned best when pHi was greater than or equal to 7.1, and homogenates of IMCD cells expressed carbonic anhydrase (CA) activity and CA II mRNA. A subgroup of IMCD cells avidly bound fluorescent peanut agglutinin (PNA); this binding became more extensive with time in culture. The PNA-labeled cells showed increased BCECF uptake, higher pHi, and more H+ pumping activity than did cells not binding PNA. They could be isolated by gel-immobilized PNA and in culture showed more CA activity and H+ pumping activity than unselected monolayers. The percentage of cells binding PNA correlated well with CA activity, indicating that this subgroup is better specialized to secrete H+. The appearance of PNA binding sites and the development of high CA activity may be characteristic of IMCD cell differentiation in culture.
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PMID:Development of H+ secretion by cultured renal inner medullary collecting duct cells. 247 40

In an effort to extend our studies on Ca2+ pumps to animal models, we developed a new monoclonal antibody (5F10) prepared against the human erythrocyte Ca2+-Mg2+-adenosinetriphosphatase (ATPase) that recognizes a protein of approximately 140 kDa in rat kidney homogenates. Enzyme-linked immunosorbent assays show that monoclonal antibody 5F10 binds purified Ca2+-Mg2+-ATPase and rat kidney membrane extracts in a concentration-dependent manner. In paraffin-embedded tissue sections, antibody 5F10 binds to an epitope in the basolateral membranes of rat kidney distal convoluted tubule principal cells. The antibody does not bind to intercalated cells. The latter cells were characterized by the presence of large amounts of carbonic anhydrase C. Polyclonal antibodies directed against chick intestinal 28-kDa vitamin D-dependent calcium binding protein (28-kDa CaBP) also bind epitopes in distal convoluted tubule cells, connecting tubules, and portions of collecting duct but not intercalated cells. Western blot and 45Ca blot analysis of renal cytosolic proteins showed that the polyclonal 28-kDa CaBP-directed antibody detects a protein which also binds calcium. Western blot analysis with monoclonal antibody 5F10 shows binding to both the authentic purified erythrocyte Ca2+ pump (approximately 138 kDa) and to tryptic fragments of this pump. Antibody JA3, previously used for staining of human kidney tubules, reacts with a different set of tryptic fragments, showing that the two antibodies are directed against different regions or conformational determinants on the pump molecule. We show that Ca2+-Mg2+-ATPase and 28-kDa CaBP are present in the principal cells of the distal convoluted tubule of the rat and are absent in intercalated cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Plasma membrane calcium pump and 28-kDa calcium binding protein in cells of rat kidney distal tubules. 255 40

In the present study we have examined ten cases of the chromophobe type renal cell carcinoma. This type of tumor is distinguished from the other carcinomas of the kidney with light cytoplasm (formerly called "hypernephroid") by (a) a positive Hale's iron colloid stain of the cytoplasm, (b) the occurrence of numerous invaginated vesicles within the cytoplasm that resemble the invaginated vesicles of intercalated cells of the collecting duct system, and (c) a positive immunoreaction of both the plasma membrane and the cytoplasm with antibodies to the epithelial membrane antigen (EMA) and carbonic anhydrase C (CAC), respectively. Unlike oncocytomas, which also express CAC and EMA, the chromophobe renal cell carcinoma does not express the erythrocyte anion exchanger band 3. These findings strongly indicate that chromophobe renal cell carcinomas as well as oncocytomas of the kidney are histogenetically related to the two populations of intercalated cells of the collecting duct system. Thus, both tumors represent examples of renal tumors which disprove the broadly accepted hypothesis that all epithelial tumors of the kidney are histogenetically related to the proximal tubule.
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PMID:The human chromophobe cell renal carcinoma: its probable relation to intercalated cells of the collecting duct. 256 18

Carbonic anhydrase is a zinc metalloenzyme widely distributed throughout the tissues of the body. This enzyme exists in a number of isozymic forms in most mammalian species. Significant advances over the past decade have been made in characterizing the nature of renal carbonic anhydrase. In the kidney, this enzyme is thought to play a pivotal role in urinary acidification and bicarbonate reabsorption. Two distinct isozymes of carbonic anhydrase have now been identified in the mammalian kidney. A soluble cytoplasmic form, similar if not identical to human erythrocyte carbonic anhydrase C, accounts for the bulk of the renal carbonic anhydrase activity. In addition, a membrane-bound form constituting only about 2--5% of the renal activity has been found in the brush border and basolateral fractions of kidney homogenates. The histochemical and immunocytochemical localization of these isozymes along the nephron and collecting duct system of various mammalian species suggests that marked heterogeneity exists. The Editorial Review examines the biochemical and morphological approaches that have been used to elucidate the nature of renal carbonic anhydrase and to assess its distribution along the urinary tubule. Possible physiological roles for the renal carbonic anhydrases are considered for the different segments of the nephron and collecting duct system.
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PMID:Renal carbonic anhydrase. 681 35

The Madin-Darby canine kidney (MDCK) cell line has been proposed as a model for studying intercalated (IC) cells of the renal cortical collecting duct. The IC cells are characterized by peanut lectin (PNA) binding capacity, carbonic anhydrase (CA) activity and Cl(-)-HCO3- exchange mediated by a band 3-related protein. It has been suggested that these properties are also expressed in MDCK cells. So far however, the nature of the specific protein involved in Cl(-)-HCO3- exchange, the type of CA isozyme and the relationship between these two characteristics and PNA binding, have not been investigated in MDCK cells by immunocytochemical methods. Using two antibodies raised against human erythrocyte band 3 protein and two against human erythrocyte CA I and II isozymes, our study provides evidence that a protein related to band 3 is expressed in about 5% of cultured MDCK cells; these band 3-positive cells do not bind PNA and are not reactive for CAI or CAII. About 30% of the MDCK cells bind PNA, two-thirds of which are also CAII-positive. A majority (about 65%) of MDCK cells is not reactive for the three markers used; their density is increased after incubation with aldosterone. These data indicate (i) that the Cl(-)-HCO3- exchange of the MDCK cells could be related to human erythrocyte band 3, (ii) that the CA activity of the MDCK cell line bears antigenic identity with the erythrocyte CA II isozyme and (iii) that the latter is always co-localized with PNA binding.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Subtypes of Madin-Darby canine kidney (MDCK) cells defined by immunocytochemistry: further evidence for properties of renal collecting duct cells. 808 17

Carbonic anhydrase (CA) facilitates the secretion of protons from renal epithelia by catalyzing the buffering of hydroxyl ions by CO2. We have previously found that inner medullary collecting duct (IMCD) cells cultured from rat kidney secrete protons and express CA II. Incubation of IMCD cells in acidic medium for 48 h has been shown to stimulate the secretion of protons by a protein synthesis-dependent process. To establish whether CA II might be involved in this process, IMCD cells were exposed to incubation media supplemented with 10(-7) M deoxycorticosterone acetate, pH 7.0 (acid) or pH 7.7 (control) for 48 h, and CA II mRNA and protein were quantitated. Part of the CA II cDNA was obtained by reverse transcription of total RNA from rat kidney followed by amplification using oligonucleotide primers derived from conserved areas in the coding regions of human, mouse, and chick CA II cDNAs in a polymerase chain reaction. By Northern analysis, steady-state levels of CA II mRNA from acid-incubated cells showed an increase of 80% compared with controls and 70% when expressed relative to a housekeeping mRNA, beta-actin. Western blot analysis using a human antibody to CA II showed an approximate doubling of CA II protein after acid incubation. By immunofluorescence microscopy, the domes of acid-incubated IMCD cells contained considerably more CA II-stained cells than found in control cultures. Thus incubation of IMCD cells in acid medium stimulates the expression of CA II mRNA and protein.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Low pH enhances expression of carbonic anhydrase II by cultured rat inner medullary collecting duct cells. 814 Dec 64

Carbonic anhydrase II (CA II), the predominant isoform of carbonic anhydrase in the kidney, is believed to be localized primarily in the cytoplasm of proximal tubule and collecting duct intercalated cells. Carbonic anhydrase facilitates H+ secretion by catalyzing the formation of HCO3- from OH- in the presence of CO2. We have shown that renal cortical CA II activity is stimulated during 4-6 days of chronic metabolic acidosis [L.P. Brion, B.J. Zavilowitz, O. Rosen, and G.J. Schwartz. Am. J. Physiol. 261 (Regulatory Integrative Comp. Physiol. 30): R1204-R1213, 1991]. The purpose of these studies was to examine under similar conditions the regulation of CA II mRNA. We obtained a major portion of the rabbit CA II cDNA by reverse transcription of total RNA from rabbit kidney followed by amplification using oligonucleotide primers prepared from conserved areas in the coding regions of human, mouse, and chick CA II cDNAs in a polymerase chain reaction (RT-PCR). The 696-bp RT-PCR product was sequenced and found to be 71-86% homologous to CA II cDNAs from the other three species. The deduced amino acid sequence agreed closely (> 97%) with a previous Edman analysis of rabbit erythrocyte CA II. Northern analysis showed expression of a approximately 1.4 kb RNA, with cortex > outer medulla > inner medulla. Steady-state mRNA expression from kidney cortex of acid-treated rabbits was about twice that from controls, when normalized to the expression of beta-actin or malate dehydrogenase. The stimulation of CA II mRNA was greater after 3 days than after 5-6 days of acid treatment. (ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Carbonic anhydrase II mRNA is induced in rabbit kidney cortex during chronic metabolic acidosis. 828 9

Carbonic anhydrase (CA) facilitates renal bicarbonate reabsorption and acid excretion. Cytosolic CA II catalyzes the buffering of intracellular hydroxyl ions by CO2, whereas membrane-bound CA IV catalyzes the dehydration of carbonic acid generated from the secretion of protons. Although CA II and IV are expressed in rabbit kidney, it is not entirely clear which segments express which isoforms. It was the purpose of this study to characterize the expression of CA II and CA IV mRNAs by specific segments of the nephron using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and to determine the effect of chronic metabolic acidosis on CA expression by those segments. Individual nephron segments (usually 1-2 mm) were isolated by microdissection and subjected to RT-PCR. Amplification was performed simultaneously for CA IV, CA II, and malate dehydrogenase (MDH), a housekeeping gene. The intensities of the PCR products were quantitated by densitometry. CA IV mRNA was expressed by S1 and S2 proximal tubules and by outer medullary collecting duct from inner stripe (OMCDi) and outer stripe and initial inner medullary collecting duct (IMCDi). CA II mRNA was expressed by S1, S2, and S3 proximal tubules, thin descending limb, connecting segment (CNT), and all collecting duct segments. Acid loading induced CA IV mRNA expression in S1 and S2 proximal tubules and in OMCDi and IMCDi. CA II mRNA was induced by acidosis in all three proximal segments and nearly all distal segments beginning with CNT. No upregulation of MDH mRNA expression occurred. These adaptive increases in CA II and IV mRNAs are potentially important in the kidney's adaptation to chronic metabolic acidosis.
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PMID:Carbonic anhydrase II and IV mRNA in rabbit nephron segments: stimulation during metabolic acidosis. 948 20

The expression of carbonic anhydrase (CA) in the quail metanephros was investigated during embryonic development. The immunohistochemical localisation of the isoenzymes CAII and CAIII was compared with the distribution of enzyme activity visualised by a histochemical cobalt-precipitation procedure. The developmental profile of CA activity was also evaluated by means of a biochemical method. The occurrence of a moderate and diffuse CAII immunostaining from the first developmental appearance of the metanephros anlage testified to an early expression of carbonic anhydrase. This finding is discussed in relation to the involvement of the enzyme in the morphogenetic mechanisms leading to the establishment both of cell polarity and epithelial phenotype. CA expression in the renal sites that are positive in adults proved to be developmentally regulated. In the collecting duct system, enzyme activity could not be identified until the time of hatching. No CA was detected at any stage examined at the sites where, in adults, enzyme occurrence has previously been interpreted as a membrane-associated CA isoform. The differentiating renal tubules displayed no CAIII immunoreactivity. It can be argued that the bulk of the enzyme activity in the embryonic metanephros is due to the cytosolic isoenzyme CAII.
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PMID:The metanephros of the quail embryo. Developmental expression of carbonic anhydrase investigated by multiple approaches. 1069 86

A major function of the kidney is to collaborate with the respiratory system to maintain systemic acid-base status within limits compatible with normal cell and organ function. It achieves this by regulating the excretion and recovery of bicarbonate (mainly in the proximal tubule) and the secretion of buffered protons (mainly in the distal tubule and collecting duct). How proximal tubular cells and distal professional proton transporting (intercalated) cells sense and respond to changes in pH, bicarbonate, and CO(2) status is a question that has intrigued many generations of renal physiologists. Over the past few years, however, some candidate molecular pH sensors have been identified, including acid/alkali-sensing receptors (GPR4, InsR-RR), kinases (Pyk2, ErbB1/2), pH-sensitive ion channels (ASICs, TASK, ROMK), and the bicarbonate-stimulated adenylyl cyclase (sAC). Some acid-sensing mechanisms in other tissues, such as CAII-PDK2L1 in taste buds, might also have similar roles to play in the kidney. Finally, the function of a variety of additional membrane channels and transporters is altered by pH variations both within and outside the cell, and the expression of several metabolic enzymes are altered by acid-base status in parts of the nephron. Thus, it is possible that a master pH sensor will never be identified. Rather, the kidney seems equipped with a battery of molecules that scan the epithelial cell environment to mount a coordinated physiologic response that maintains acid-base homeostasis. This review collates current knowledge on renal acid-base sensing in the context of a whole organ sensing and response process.
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PMID:Molecular mechanisms of acid-base sensing by the kidney. 2236 4

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