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  • 1
    Online Resource
    Online Resource
    American Physiological Society ; 1993
    In:  American Journal of Physiology-Renal Physiology Vol. 265, No. 2 ( 1993-08-01), p. F327-F332
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 265, No. 2 ( 1993-08-01), p. F327-F332
    Abstract: We recently isolated a cDNA encoding a Na+/Ca2+ exchanger from rabbit kidney that was highly similar to the canine cardiac sarcolemmal Na+/Ca2+ exchanger. In the present study, we used two different antibodies to the exchanger to identify the protein and establish its cellular and subcellular localization in the kidney. The first antibody was prepared against a fusion protein consisting of 190 amino acids of the large, presumably intracellular loop of the rabbit renal exchanger fused to the maltose-binding protein. The second was a monoclonal antibody generated against the isolated purified canine cardiac sarcolemmal exchanger. To identify the Na+/Ca2+ exchanger protein, we performed immunoblot analysis against a membrane vesicle preparation from rabbit kidney cortex. Both antibodies immunoblotted proteins of 120 and 70 kDa that are known to be associated with the exchanger. Indirect immunofluorescence revealed that both antisera labeled the basolateral surface of the majority of cells in the connecting tubule (CNT). Since the phase-dense (intercalated) cells in the CNT were not stained, this suggested that the labeled cells were CNT cells. No labeling was detected in other nephron segments with the exception of occasional faint staining of the majority cell population of the cortical collecting duct. The fact that we did not detect labeling in other nephron segments is consistent with either 1) the absence of expression of the Na+/Ca2+ exchanger in these segments, 2) the expression of the exchanger in levels below the threshold of detection of the two antibodies used in this study, or 3) the exchanger in these segments is represented by a different isoform.(ABSTRACT TRUNCATED AT 250 WORDS)
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1993
    detail.hit.zdb_id: 1477287-5
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  • 2
    Online Resource
    Online Resource
    American Physiological Society ; 1995
    In:  American Journal of Physiology-Renal Physiology Vol. 268, No. 5 ( 1995-05-01), p. F815-F820
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 268, No. 5 ( 1995-05-01), p. F815-F820
    Abstract: The neonatal proximal tubule has a lower rate of bicarbonate absorption and Na+/H+ antiporter activity than the proximal tubule of adult animals. Two isoforms of the Na+/H+ antiporter have been localized to the proximal tubule. NHE3 is located on the apical membrane, whereas NHE1, the isoform found on most mammalian cells, is present on the basolateral membrane. The Na+/H+ antiporter isoforms that increase with renal maturation are unknown. The purpose of the present study was to examine the maturation of rabbit renal cortical NHE3 and NHE1 mRNA and protein abundance and to determine whether the rate of maturation of these isoforms was affected by glucocorticoids. Renal cortex from neonatal rabbits (1 wk) had approximately one-fourth the NHE3 mRNA and protein abundance as that from adult animals. Renal cortical NHE1 mRNA and protein abundance did not change significantly during maturation. Glucocorticoids have been shown to accelerate the maturation of neonatal bicarbonate absorption and apical membrane Na+/H+ antiporter activity. Daily subcutaneous administration of dexamethasone starting at 4 days of age (10 micrograms/100 g body wt) for 3 days and 2 h before being killed resulted in a twofold increase in NHE3 mRNA abundance and a threefold increase in NHE3 protein abundance. NHE1 mRNA and protein abundance were unaffected. These data show that there is selective maturation of NHE3 during renal cortical development, which can be accelerated by administration of glucocorticoids.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1995
    detail.hit.zdb_id: 1477287-5
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  • 3
    Online Resource
    Online Resource
    Proceedings of the National Academy of Sciences ; 1992
    In:  Proceedings of the National Academy of Sciences Vol. 89, No. 15 ( 1992-08), p. 6698-6702
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 89, No. 15 ( 1992-08), p. 6698-6702
    Abstract: Using antibodies isolated from glomeruli of nephritic rats we have previously identified a 330-kDa cell surface glycoprotein (gp330) as a major pathogenic antigen of Heymann nephritis (HN), an experimental model of human membranous glomerulonephritis. Recently, we have isolated a cDNA clone, C14, encoding a polypeptide that contains a pathogenic epitope of HN responsible for the initiation of the disease. Subsequently, another protein, alpha 2-macroglobulin receptor-associated protein (alpha 2-MRAP), which is a subunit of the receptor for human alpha 2-macroglobulin/low density lipoprotein receptor-related protein (LRP), was shown to possess a high degree of sequence homology to the C14 protein (C14p). In this report, we have investigated the relationship between gp330, C14p, and alpha 2-MRAP. Immunoprecipitation studies demonstrate that gp330 forms a heterodimeric association with a 44-kDa polypeptide that is stable to detergent extraction and long-term centrifugation. Further, immunoblotting analysis on the purified complex indicates that the 44-kDa associated protein shares immunological identity to C14p and alpha 2-MRAP. In addition, antibodies eluted from glomeruli of HN rats and antibodies to a C14 fusion protein immunoprecipitated gp330 and the 44-kDa protein, demonstrating that the epitopes responsible for the initial events of HN are accessible within the complex. Based on these data, three models are proposed to explain how pathogenic epitopes in the gp330-44-kDa, HN antigenic complex may be presented at the cell surface and initiate the onset of HN.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    RVK:
    RVK:
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1992
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    American Physiological Society ; 1993
    In:  American Journal of Physiology-Renal Physiology Vol. 264, No. 1 ( 1993-01-01), p. F141-F148
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 264, No. 1 ( 1993-01-01), p. F141-F148
    Abstract: Thiazide diuretics increase urinary NaCl excretion primarily by inhibiting Na and Cl transport across the apical membrane of cells in the renal distal tubule. Although these diuretics bind to a membrane protein that couples transport of Na and Cl directly, the molecular nature of this transporter and its localization in the mammalian kidney remain controversial. The present experiments were designed to develop monoclonal antibodies to the high-affinity thiazide diuretic receptor to investigate its molecular characteristics and its cellular and subcellular localization in rabbit kidney. Mice were immunized with high-affinity thiazide diuretic receptors that had been partially purified from rabbit kidney cortex. Resulting hybridomas were screened for the ability to immunoprecipitate thiazide diuretic receptors that were labeled with the thiazide-like diuretic [3H]metolazone. A single hybridoma (MAb JM5) produced antibodies capable of immunoprecipitating up to 80% of the labeled thiazide receptors from solubilized renal cortical membranes. MAb JM5 reacted with a 125-kDa protein on Western blots of solubilized renal cortical apical membranes. It stained the apical membrane of cells in the distal convoluted and connecting tubule but did not stain proximal tubules, glomeruli, or interstitial structures. Less intense staining of apical membranes of principal cells in the collecting tubule and a subpopulation of cells in the thick ascending limb were also present. These results indicate that the high-affinity thiazide diuretic receptor comprises a 125-kDa protein that localizes to the apical membrane of cells in the renal distal tubule.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1993
    detail.hit.zdb_id: 1477287-5
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  • 5
    Online Resource
    Online Resource
    American Physiological Society ; 1984
    In:  American Journal of Physiology-Cell Physiology Vol. 247, No. 3 ( 1984-09-01), p. C204-C216
    In: American Journal of Physiology-Cell Physiology, American Physiological Society, Vol. 247, No. 3 ( 1984-09-01), p. C204-C216
    Abstract: The cellular ultrastructure of the renal distal nephron of the salamander, Amphiuma means, was examined by electron-microscopic and stereological techniques before and after exposure to potassium in the ambient environment. The distal nephron of Amphiuma is composed of three ultrastructurally distinct segments: early distal (or diluting segment), late distal, and collecting tubule. The early distal tubule structurally resembles the mammalian thick ascending limb of Henle's loop. Large renin-like granules are present in the smooth muscle cells of the afferent arteriole in the vicinity of the early distal tubule, suggesting the presence of a rudimentary juxtaglomerular apparatus. Late distal tubules are composed of one large cell type characterized by extensive basal membrane invaginations, often extending to the luminal membrane. Collecting tubules contain principal and intercalated cells that are ultrastructurally similar to cells of the mammalian cortical collecting tubule. Exposure to potassium had no effect on the ultrastructure of early distal cells but led to a sharp increase in the basolateral membrane surface density of principal cells in the collecting tubule (1.17 +/- 0.08-1.63 +/- 0.13 micron2/micron3). Potassium adaptation leads to a similar structural response in the mammalian collecting tubule. Since Amphiuma collecting tubules can be isolated and perfused in vitro and impaled with ion- and voltage-sensitive microelectrodes, the observed structural adaptation suggests that the collecting tubule may be a useful preparation to study the cellular mechanisms of potassium adaptation.
    Type of Medium: Online Resource
    ISSN: 0363-6143 , 1522-1563
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1984
    detail.hit.zdb_id: 1477334-X
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    Rockefeller University Press ; 1993
    In:  The Journal of cell biology Vol. 121, No. 3 ( 1993-05-01), p. 579-586
    In: The Journal of cell biology, Rockefeller University Press, Vol. 121, No. 3 ( 1993-05-01), p. 579-586
    Abstract: The gamma subunit of the Na,K-ATPase is a small membrane protein that copurifies with the alpha and beta subunits of the enzyme. Strong evidence that the gamma subunit is a component of the Na,K-ATPase comes from studies indicating that the subunit is involved in forming the site for cardiac glycoside binding. We have isolated and characterized the cDNAs coding the gamma subunit from several species. The gamma subunit is a highly conserved protein consisting of 58 amino acids with a molecular weight of 6500. Hydropathy analysis reveals the presence of a single hydrophobic domain that is sufficient to cross the membrane. There are no sites for N-linked glycosylation. Northern blot analysis revealed that the gamma subunit mRNA is expressed in a tissue-specific fashion and is present in all tissues characterized. gamma-specific antibodies have been used to verify that the sequenced protein is the same protein labeled by [3H]nitroazidobenzoyl-ouabain (NAB-ouabain), and that this protein, the gamma subunit of the Na,K-ATPase, has a distribution pattern along nephron segments that is identical with the alpha subunit. In addition, coimmunoprecipitation of the alpha, beta and gamma subunits demonstrate specific association of the subunits. These results are consistent with the notion that the gamma subunit is specifically associated with and may be an important component of the Na,K-ATPase.
    Type of Medium: Online Resource
    ISSN: 0021-9525 , 1540-8140
    RVK:
    Language: English
    Publisher: Rockefeller University Press
    Publication Date: 1993
    detail.hit.zdb_id: 1421310-2
    SSG: 12
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  • 7
    Online Resource
    Online Resource
    Cambridge University Press (CUP) ; 1982
    In:  Proceedings, annual meeting, Electron Microscopy Society of America Vol. 40 ( 1982-08-13), p. 170-171
    In: Proceedings, annual meeting, Electron Microscopy Society of America, Cambridge University Press (CUP), Vol. 40 ( 1982-08-13), p. 170-171
    Abstract: Although the surface distal tubule of Amphiuma means has been used in transport and electrophysiology studies, a detailed description of its ultrastructure is lacking. In vitro microperfusion studies have identified three physiologically distinct segments. This study describes the morphology of the distal tubule of Amphiuma by transmission and scanning electron microscopy. Kidneys of ten animals were perfused via the aortic and portal vessels with amphibian ringers followed by fixative containing 1% paraformaldehyde, 1.25% glutaraldehyde, 0.05 M sucrose, 2% T40 Dextran, in 0.05 M Na cacodylate buffer, pH 7.2. For TEM, the kidneys were processed as described previously. For SEM, the tissue was osmicated, dehydrated and critical point dried using CO 2
    Type of Medium: Online Resource
    ISSN: 0424-8201 , 2690-1315
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 1982
    SSG: 11
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  • 8
    Online Resource
    Online Resource
    American Physiological Society ; 1995
    In:  American Journal of Physiology-Cell Physiology Vol. 269, No. 6 ( 1995-12-01), p. C1496-C1505
    In: American Journal of Physiology-Cell Physiology, American Physiological Society, Vol. 269, No. 6 ( 1995-12-01), p. C1496-C1505
    Abstract: The Na-K-Cl cotransporter (NKCC) is present in most animal cells where it functions in cell volume homeostasis and epithelial salt transport. We developed six monoclonal antibodies (designated T4, T8, T9, T10, T12, and T14) against a fusion protein fragment encompassing the carboxy-terminal 310 amino acids of the human colonic NKCC. These T antibodies selectively recognized putative NKCC proteins in a diverse variety of animal tissues. Western blot analysis of membranes isolated from 23 types of cells identified single bands of immunoreactive protein ranging in mass from 146 to 205 kDa. The amount of immunoreactive protein detected in these cells correlated with loop diuretic binding site density. Proteins identified previously as Na-K-Cl cotransporters by loop diuretic photoaffinity labeling were mutually recognized by multiple T antibodies. Most of the T antibodies effectively immunoprecipitated the denatured form of the NKCC protein. Immunocytochemical studies on the rabbit parotid gland demonstrated that NKCC is restricted to the basolateral margin of the acinar cells and absent from the ducts, in accord with the central role of Na-K-Cl cotransport in chloride secretion. In the rabbit kidney, NKCC was localized to the apical membrane of thick ascending limb cells, consistent with its role in chloride reabsorption.
    Type of Medium: Online Resource
    ISSN: 0363-6143 , 1522-1563
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1995
    detail.hit.zdb_id: 1477334-X
    SSG: 12
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  • 9
    Online Resource
    Online Resource
    American Physiological Society ; 1993
    In:  American Journal of Physiology-Renal Physiology Vol. 265, No. 5 ( 1993-11-01), p. F736-F742
    In: American Journal of Physiology-Renal Physiology, American Physiological Society, Vol. 265, No. 5 ( 1993-11-01), p. F736-F742
    Abstract: Na+/H+ exchangers in the brush-border (luminal, apical) membrane of renal proximal tubules are responsible for active, transcellular reabsorption of NaHCO3 and NaCl. Although well characterized kinetically, the protein that mediates Na+/H+ exchange in the renal brush border has not been identified. Several Na+/H+ exchanger genes, including NHE1, NHE2, NHE3, and NHE4, are expressed in the kidney. To identify the NHE3 gene product and to determine its cellular and subcellular localization in the rabbit kidney, an NHE3-isoform-specific antibody was prepared. Guinea pigs were immunized with purified fusion protein containing the carboxy-terminal 40 amino acids of NHE3 (fpNHE3-C40). After affinity purification, immune sera demonstrated specific reactivity to the NHE3 sequence within the fusion protein as well as to an 80-kDa polypeptide expressed in NHE3-transfected LAP1 cells. Western blot analysis showed that anti-fpNHE3-C40 specifically reacted with an 80-kDa protein that is relatively enriched in renal brush-border membrane compared with basolateral membrane. Immunocytochemical studies confirmed that the Na+/H+ exchanger isoform NHE3 is expressed along the microvillar membrane of the brush border of proximal tubule cells in the rabbit kidney.
    Type of Medium: Online Resource
    ISSN: 1931-857X , 1522-1466
    Language: English
    Publisher: American Physiological Society
    Publication Date: 1993
    detail.hit.zdb_id: 1477287-5
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  • 10
    Online Resource
    Online Resource
    Elsevier BV ; 2006
    In:  Kidney International Vol. 69, No. 10 ( 2006-05), p. 1717-1721
    In: Kidney International, Elsevier BV, Vol. 69, No. 10 ( 2006-05), p. 1717-1721
    Type of Medium: Online Resource
    ISSN: 0085-2538
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2006
    detail.hit.zdb_id: 2007940-0
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