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Rao US, Baker JM, Pluznick JL, Balachandran P. Role of intracellular Ca2+ in the expression of the amiloride-sensitive epithelial sodium channel. Cell Calcium 2004; 35:21-8. [PMID: 14670368 DOI: 10.1016/s0143-4160(03)00157-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The amiloride-sensitive epithelial sodium channel (ENaC), a multimeric plasma membrane protein composed of alpha-, beta-, and gamma-ENaC subunits, mediates Na(+) reabsorption in epithelial tissues, including the distal nephron, colon, lung, and secretory glands, and plays a critical role in pathophysiology of essential hypertension and cystic fibrosis (CF). The function of ENaC is tightly regulated by signals elicited by aldosterone, vasopressin, agents that increase intracellular cAMP levels, ions, ion channels, G-protein-coupled mechanisms, and cytoskeletal proteins. In this paper, the effects of Ca(2+) on the expression of the human ENaC subunits expressed in human embryonic kidney cells (HEK-293 cells) were examined. Incubation of cells with increased extracellular Ca(2+) and treatment of cells with A23187 and thapsigargin stimulated the expression of the monomeric ENaC subunits. Treatment of cells with Ca(2+)-chelating agents, EGTA and BAPTA-AM, reduced the levels of ENaC subunit expression. The pulse-chase experiments suggested that a rise in the intracellular Ca(2+) increases the ENaC subunit expression. Immunoblot analysis using the anti-ubiquitin antibody indicated that ENaC undergoes ubiquitination. A correlation between the processes that regulate ENaC function with the intracellular Ca(2+) was discussed.
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Affiliation(s)
- U Subrahmanyeswara Rao
- Department of Biochemistry and Molecular Biology, 984525 Nebraska Medical Center, Omaha, NE 68198-4525, USA.
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Elbrønd VS, Dantzer V, Skadhauge E. Differences in epithelial morphology correlate to Na(+)-transport: a study of the proximal, mid, and distal regions of the coprodeum from hens on high and low NaCl diet. J Morphol 1999; 239:75-86. [PMID: 9918098 DOI: 10.1002/(sici)1097-4687(199901)239:1<75::aid-jmor5>3.0.co;2-d] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
A study was performed to correlate regional morphology and amiloride inhibitable Na(+)-transport in the coprodeal epithelium in hens, Gallus domesticus, on low-NaCl diet and in controls. Proximal (close to colon), mid and distal (close to urodeum) regions were examined using light microscopy, transmission- and scanning electron microscopy. Na(+)-transport was measured electrophysiologically in Ussing-chambers in the proximal and distal regions. The epithelium, simple and columnar, is composed of absorptive intestinal epithelial cells, goblet cells, brush cells, migrating lymphoid cells, and enteroendocrine cells. Brush cells, identified in avians for the first time, occur in highest number in the proximal part of the coprodeum in low-NaCl hens. Na(+)-transport is high in the low-NaCl hens, ranging from 347 microA/cm2 (proximal) to 187 microA/cm2 (distal). In control hens, which correspond to hens on high-NaCl diet, it is low in all regions (0-4 microA/cm2). Absorptive intestinal epithelial cells as well as brush cells adapt to variations in transepithelial Na(+)-transport by regulating height and packing density of their microvilli, number, size, and localization of apical vesicles, and the width of the intercellular space. Regional differences in the epithelial cell composition and ultrastructure are closely correlated to transepithelial Na(+)-transport but only in low-NaCl hens, as controls do not show these variations.
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Affiliation(s)
- V S Elbrønd
- Department of Anatomy and Physiology, Royal Veterinary and Agricultural University, Frederiksberg C, Denmark.
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Goldstein O, Asher C, Cragoe E, Kleyman TR, Garty H. An aldosterone regulated chicken intestine protein with high affinity to amiloride. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART A, PHYSIOLOGY 1997; 118:201-8. [PMID: 9366044 DOI: 10.1016/s0300-9629(97)00067-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The pattern of chicken intestine amiloride-binding proteins was determined using the photoreactive amiloride analogue 2'-methoxy-5'-nitrobenzamil (NMBA) and a polyclonal anti-amiloride antibody. At 10(-7)M, NMBA inhibits approximately 62% of the Na+ channel activity. At this concentration the amiloride analogue labels a number of membrane proteins, and in particular a 40-45 kDa polypeptide denoted ABP40. Incorporation of NMBA into ABP40 could be prevented by a 100-fold excess of benzamil, but not by a 1000-fold excess of 5-(N-ethyl-N-isopropyl)-amiloride. Labeling of ABP40 was intense in membranes derived from salt-deprived chickens and approximately 5-fold weaker in membranes from salt-repleted animals. Because of its small size, ABP40 is not likely to be an avian Na+ channel subunit, yet this amiloride-binding protein could be involved in the response to aldosterone.
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Affiliation(s)
- O Goldstein
- Department of Membrane Research And Biophysics, Weizmann Institute Of Science, Rehovot, Israel
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Siragy HM, Jaffa AA, Margolius HS. Bradykinin B2 receptor modulates renal prostaglandin E2 and nitric oxide. Hypertension 1997; 29:757-62. [PMID: 9052892 DOI: 10.1161/01.hyp.29.3.757] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Bradykinin and lys-bradykinin generated intrarenally appear to be important renal paracrine hormones. However, the renal effects of endogenously generated bradykinin are still not clearly defined. In this study, we measured acute changes in renal excretory and hemodynamic functions and renal cortical interstitial fluid levels of bradykinin, prostaglandin E2, and cGMP in response to an acute intrarenal arterial infusion of the bradykinin B2 receptor antagonist Hoe 140 (icatibant), cyclooxygenase inhibitor indomethacin, or nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) given individually or combined in uninephrectomized, conscious dogs (n=10) in low sodium balance. Icatibant caused a significant decrease in urine flow, urinary sodium excretion, and renal plasma flow rate (each P<.001). Glomerular filtration rate did not change during icatibant administration. Icatibant produced an unexpected large increase in renal interstitial fluid bradykinin (P<.0001) while decreasing renal interstitial fluid prostaglandin E2 and cGMP (each P<.001). Both indomethacin and L-NMMA when given individually caused significant antidiuresis and antinatriuresis and decreased renal blood flow (each P<.001). Glomerular filtration rate decreased during L-NMMA administration (P<.001) and did not change during indomethacin administration. Combined administration of icatibant and indomethacin or L-NMMA caused significant decreases in renal excretory and hemodynamic functions, which were not different from changes observed with icatibant alone. The failure of icatibant to change renal function after inhibition of cyclooxygenase and nitric oxide synthase activity suggests that the effects of kinin B2 receptor are mediated by intrarenal prostaglandin E2 and nitric oxide generation. The increase in renal interstitial fluid bradykinin during icatibant requires further study of possible alterations in kinin synthesis, degradation, or clearance as a result of B2 receptor blockade.
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Affiliation(s)
- H M Siragy
- Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville 22908, USA
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Odya CE, Carlin RJ, Yapa RD, Soltani-Tehrani B. Immunoassays for des-Arg9-bradykinin. JOURNAL OF IMMUNOASSAY 1993; 14:227-40. [PMID: 8294567 DOI: 10.1080/15321819308019852] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Splenocytes from a female, BALB/c mouse immunized with bradykinin conjugated to ovalbumin with toluene diisocyanate were fused with mouse myeloma cells, X63/Ag8.653, using polyethylene glycol. Seventy-nine hybridomas were identified by ELISA to be making kinin reactive antibodies. In preliminary specificity studies it was determined that all of these hybridomas were producing antibodies more reactive with des-Arg9-bradykinin than with bradykinin. ELISAs were developed with the five clones that displayed the highest affinities for des-Arg9-bradykinin. Radioimmunoassays were developed for 3 of these 5 clones as well as with 5 monoclonal antibodies previously described (Odya and Lee 1990). The most sensitive des-Arg9-bradykinin assay developed was a radioimmunoassay in which carboxypeptidase B-treated [Tyr5]-bradykinin was the labeled antigen, clone OLNBK-5 was the antibody, and dextran-coated charcoal was used to separate bound from free radioactivity. The concentration of des-Arg9-bradykinin that inhibited 50% of the radioactive peptide binding was 0.08 +/- 0.03 nM. The relative specificity of this assay (des-Arg9-bradykinin = 100%) was: 29% bradykinin and about 1% with each of the following: lysyl-bradykinin, methionyl-lysyl-bradykinin, des-Arg1-bradykinin and des-Phe8-Arg9-bradykinin.
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Affiliation(s)
- C E Odya
- Medical Sciences Program, Indiana University School of Medicine, Bloomington 47405
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Goldstein O, Asher C, Barbry P, Cragoe E, Clauss W, Garty H. An epithelial high-affinity amiloride-binding site, different from the Na+ channel. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53036-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Smith PR, Bradford AL, Dantzer V, Benos DJ, Skadhauge E. Immunocytochemical localization of amiloride-sensitive sodium channels in the lower intestine of the hen. Cell Tissue Res 1993; 272:129-36. [PMID: 8386985 DOI: 10.1007/bf00323578] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We have used polyclonal antibodies generated against purified bovine renal amiloride-sensitive Na+ channels to localize amiloride-sensitive Na+ channels within the lower intestine (colon and coprodeum) of the hen. These antibodies cross-reacted with two polypeptides exhibiting M(r)'s of 235 and 150 kDa on immunoblots of detergent-solubilized apical membrane fractions from both the colon and coprodeum. The apparent molecular masses of theses polypeptides are in agreement with the M(r)'s of 2 of the subunits of the renal high amiloride-affinity Na+ channel, namely the alpha and the beta (= amiloride binding) subunits. The cellular distribution of Na+ channels was determined by immunoperoxidase and indirect immunofluorescence cytochemical techniques. The apical (luminal) membrane and cytoplasm of villar principal cells in both colon and coprodeum exhibited immunoreactivity, whereas goblet cells were negative. Both principal and goblet cells of the crypts were also negative. We conclude that the amiloride-sensitive Na+ channels are localized to the principal cells of the intestinal villi and that these cells are responsible for intestinal Na+ absorption.
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Affiliation(s)
- P R Smith
- Department of Physiology and Biophysics, University of Alabama, Birmingham
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Venglarik CJ, Singh AK, Wang R, Bridges RJ. Trinitrophenyl-ATP blocks colonic Cl- channels in planar phospholipid bilayers. Evidence for two nucleotide binding sites. J Gen Physiol 1993; 101:545-69. [PMID: 8389396 PMCID: PMC2216774 DOI: 10.1085/jgp.101.4.545] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Outwardly rectifying 30-50-pS Cl- channels mediate cell volume regulation and transepithelial transport. Several recent reports indicate that rectifying Cl- channels are blocked after addition of ATP to the extracellular bath (Alton, E. W. F. W., S. D. Manning, P. J. Schlatter, D. M. Geddes, and A. J. Williams. 1991. Journal of Physiology. 443:137-159; Paulmichl, M., Y. Li, K. Wickman, M. Ackerman, E. Peralta, and D. Clapham. 1992. Nature. 356:238-241). Therefore, we decided to conduct a more detailed study of the ATP binding site using a higher affinity probe. We tested the ATP derivative, 2',3',O-(2,4,6-trinitrocyclohexadienylidene) adenosine 5'-triphosphate (TNP-ATP), which has a high affinity for certain nucleotide binding sites. Here we report that TNP-ATP blocked colonic Cl- channels when added to either bath and that blockade was consistent with the closed-open-blocked kinetic model. The TNP-ATP concentration required for a 50% decrease in open probability was 0.27 microM from the extracellular (cis) side and 20 microM from the cytoplasmic (trans) side. Comparison of the off rate constants revealed that TNP-ATP remained bound 28 times longer when added to the extracellular side compared with the cytoplasmic side. We performed competition studies to determine if TNP-ATP binds to the same sites as ATP. Addition of ATP to the same bath containing TNP-ATP reduced channel amplitude and increased the time the channel spent in the open and fast-blocked states (i.e., burst duration). This is the result expected if TNP-ATP and ATP compete for block, presumably by binding to common sites. In contrast, addition of ATP to the bath opposite to the side containing TNP-ATP reduced amplitude but did not alter burst duration. This is the result expected if opposite-sided TNP-ATP and ATP bind to different sites. In summary, we have identified an ATP derivative that has a nearly 10-fold higher affinity for reconstituted rectifying colonic Cl- channels than any previously reported blocker (Singh, A. K., G. B. Afink, C. J. Venglarik, R. Wang, and R. J. Bridges. 1991. American Journal of Physiology. 260 [Cell Physiology. 30]:C51-C63). Thus, TNP-ATP should be useful in future studies of ion channel nucleotide binding sites and possibly in preliminary steps of ion channel protein purification. In addition, we have obtained good evidence that there are at least two nucleotide binding sites located on opposite sides of the colonic Cl- channel and that occupancy of either site produces a blocked state.
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Affiliation(s)
- C J Venglarik
- Department of Physiology and Biophysics, University of Alabama, Birmingham
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Oh Y, Matalon S, Kleyman T, Benos D. Biochemical evidence for the presence of an amiloride binding protein in adult alveolar type II pneumocytes. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)36990-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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10
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Bauer ML, Beckman JS, Bridges RJ, Fuller CM, Matalon S. Peroxynitrite inhibits sodium uptake in rat colonic membrane vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1104:87-94. [PMID: 1550856 DOI: 10.1016/0005-2736(92)90135-9] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Peroxynitrite (ONOO-) is a potent oxidizing agent that initiates lipid peroxidation and sulfhydryl oxidation and may be responsible for a portion of the cytotoxicity attributed to superoxide anion (.O2-). We quantified the extent to which ONOO-, xanthine plus xanthine oxidase (XO) and hydrogen peroxide (H2O2), decreased sodium (Na+) uptake into membrane vesicles derived from colonic cells of dexamethasone-treated rats. Carrier-free 22Na+ uptake into vesicles was measured in the presence of an inside-negative membrane potential, produced by the addition of the potassium ionophore valinomycin (10 microM) after removal of all external potassium by cation exchange chromatography. Preincubation of vesicles with either 100 microM or 1 mM ONOO- for 30 s decreased the amiloride-blockable fraction of Na+ uptake by 27 +/- 7% and 65 +/- 2%, respectively (means +/- S.E.; n greater than or equal to 5; P less than 0.05 from control). However, the amiloride-insensitive part of Na+ uptake was not affected, indicating that there was no overt destruction of these vesicles by these ONOO- concentrations. Decomposed ONOO-, hydrogen peroxide (1 microM-10 mM), or xanthine (500 microM) plus XO (10-30 mU/ml), either in the absence or in the presence of 100 microM FeEDTA, did not decrease Na+ uptake. These data suggest that ONOO- is a potent injurious agent that can compromise Na+ uptake across epithelial cells, possibly by damaging Na+ channels.
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Affiliation(s)
- M L Bauer
- Department of Pediatrics, University of Alabama, Birmingham 35223
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Benos DJ, Cunningham S, Baker RR, Beason KB, Oh Y, Smith PR. Molecular characteristics of amiloride-sensitive sodium channels. Rev Physiol Biochem Pharmacol 1992; 120:31-113. [PMID: 1325667 DOI: 10.1007/bfb0036122] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- D J Benos
- Department of Physiology and Biophysics, University of Alabama, Birmingham 35294
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12
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Fuller CM, Benos DJ. The physiology and biochemistry of sodium and chloride permeability pathways in epithelia. J Nutr Biochem 1991. [DOI: 10.1016/0955-2863(91)90091-i] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Civan MM, Oler A, Peterson-Yantorno K, George K, O'Brien TG. Ca(2+)-independent form of protein kinase C may regulate Na+ transport across frog skin. J Membr Biol 1991; 121:37-50. [PMID: 1646890 DOI: 10.1007/bf01870649] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Activators of protein kinase C (PKC) stimulate Na+ transport (JNa) across frog skin. We have examined the effect of Ca2+ on PKC stimulation of JNa. Both the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) and the diacyl-glycerol sn-1,2-dioctanoylglycerol (DiC8) were used as PKC activators. Blocking Ca2+ entry into the cytosol (either from external or internal stores) reduced the subsequent natriferic effect of the PKC activators. This negative interaction did not simply reflect saturation of activation of the apical Na+ channels, since the stimulations produced by blocking Ca2+ entry and adding cyclic AMP were simply additive. The Ca2+ dependence of the natriferic effect could have reflected either a direct action of cytosolic Ca2+ on PKC or an indirect action on the final receptor site (the Na+ channel). To distinguish between these possibilities, the TPA- and phospholipid-dependent kinase activity of broken-cell preparations was assayed. The kinase activity was not stimulated by physiological levels of Ca2+, and in fact was inhibited at millimolar concentrations of Ca2+. We conclude that the effects of Ca2+ on the natriferic response to PKC activators are indirect. Reducing cytosolic uptake of Ca2+ may have stimulated Na+ transport by a chemical modification of the apical channels observed in other tight epithelia. The usual stimulation of Na+ transport produced by PKC activators in frog skin may reflect the operation of a nonconventional form of PKC. This enzyme is Ca2+ independent and seems related to the nPKC or PKC epsilon observed in other systems.
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Affiliation(s)
- M M Civan
- Wistar Institute, Philadelphia, Pennsylvania
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Rajendran VM, Kashgarian M, Binder HJ. Aldosterone induction of electrogenic sodium transport in the apical membrane vesicles of rat distal colon. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)51514-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Moran A, Asher C, Cragoe EJ, Garty H. Conductive sodium pathway with low affinity to amiloride in LLC-PK1 cells and other epithelia. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)77676-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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