scholarly journals Thyroid hormone stimulates the renal Na/H exchanger NHE3 by transcriptional activation

1999 ◽  
Vol 276 (1) ◽  
pp. C102-C108 ◽  
Author(s):  
Adriana Cano ◽  
Michel Baum ◽  
Orson W. Moe
Keyword(s):  
Thyroid Hormone ◽  
Transcriptional Activation ◽  
Transcript Abundance ◽  
Epithelial Cell Line ◽  
Protein Abundance ◽  
Renal Epithelial Cell ◽  
Opossum Kidney ◽  
Ok Cells ◽  
Transcript Stability ◽  
Renal Epithelial Cell Line

Thyroid hormone stimulates renal proximal tubule NaCl and NaHCO3 absorption in part by activating the apical membrane Na/H exchanger NHE3. We used a renal epithelial cell line, the opossum kidney (OK) cell, to define the mechanism by which 3,5,3′-triiodothyronine (T3) increases NHE3 activity. T3 stimulated NHE3 activity, an effect that was blocked by inhibition of cellular transcription or translation. The increase in activity was associated with increases in steady-state cell surface and total cellular NHE3 protein and NHE3 transcript abundance. T3stimulated transcription of the NHE3 gene and had no effect on NHE3 transcript stability. The transcriptional activity of the 5′-flanking region of the rat NHE3 gene was stimulated by T3 when expressed in OK cells. When heterologously expressed rat NHE3 transcript levels were clamped constant with a constitutive promoter in OK cells, T3 has no effect on rat NHE3 protein abundance, suggesting the absence of regulation of NHE3 protein stability or translation. These studies demonstrate that T3 stimulates NHE3 activity by activating NHE3 gene transcription and increasing NHE3 transcript and protein abundance.

scholarly journals Locally formed 5-hydroxytryptamine stimulates phosphate transport in cultured opossum kidney cells and in rat kidney

1996 ◽  
Vol 320 (2) ◽  
pp. 615-621 ◽  
Author(s):  
Zakia HAFDI ◽  
Sylvianne COUETTE ◽  
Etienne COMOY ◽  
Dominique PRIE ◽  
Claude AMIEL ◽  
...  
Keyword(s):  
Rat Kidney ◽  
Mrna Level ◽  
Phosphate Transport ◽  
Inhibitory Effect ◽  
Acid Decarboxylase ◽  
Epithelial Cell Line ◽  
Renal Epithelial Cell ◽  
Opossum Kidney ◽  
Amino Acid Decarboxylase ◽  
Ok Cells

Renal proximal tubular cells have been shown to express aromatic l-amino acid decarboxylase (l-AAAD), which converts l-dopa into dopamine and 5-hydroxytryptophan [(OH)Trp] into 5-hydroxytryptamine (5-HT; serotonin). Because 5-HT receptors have been demonstrated in proximal cells, we hypothesized that 5-HT may act as an autocrine/paracrine modulator of proximal transport. We evaluated this possibility in opossum kidney (OK) cells, a renal epithelial cell line with a proximal phenotype expressing 5-HT1B receptors, and in intact anaesthetized rats. 5-HT synthesis by OK cells increased with incubation time and (OH)Trp concentration, and was abolished by benserazide, an l-AAAD inhibitor. 5-HT reversed parathyroid hormone (PTH)-induced cAMP accumulation in a pertussis toxin-sensitive manner and reduced the PTH inhibition of Pi uptake without affecting the NaPi-4 mRNA level. The effects of 5-HT on cAMP generation and Na–Pi co-transport were reproduced by (OH)Trp, except in the presence of benserazide, and by l-propranolol and dihydroergotamine, two 5-HT1B receptor agonists. In rats, (OH)Trp and dihydroergotamine decreased fractional Pi excretion. Benserazide abolished the effect of (OH)Trp but not that of dihydroergotamine. In conclusion: (i) locally generated 5-HT blunts the inhibitory effect of PTH on Na–Pi co-transport in OK cells; (ii) endogenous 5-HT decreases Pi excretion in rats; and (iii) 5-HT is a paracrine modulator involved in the physiological regulation of renal Pi transport.

Insulin stimulates phosphate transport in opossum kidney epithelial cells

1990 ◽  
Vol 258 (6) ◽  
pp. F1592-F1598 ◽  
Author(s):  
M. I. Abraham ◽  
J. A. McAteer ◽  
S. A. Kempson
Keyword(s):  
Insulin Action ◽  
Phosphate Uptake ◽  
Phosphate Transport ◽  
In Vivo Studies ◽  
Epithelial Cell Line ◽  
Protein Synthesis Inhibitors ◽  
Renal Epithelial Cell ◽  
Opossum Kidney ◽  
Ok Cells

Insulin is antiphosphaturic in vivo and this effect is due, in part, to increased Na(+)-dependent phosphate uptake across the luminal brush-border membrane of the proximal tubule. The intracellular mechanism is not understood. The present study shows that the stimulatory effect of insulin on phosphate transport can be reproduced in opossum kidney (OK) cells, suggesting that this established renal epithelial cell line may be a good model for further studies on insulin action on renal phosphate transport. The stimulation by insulin was dose related when insulin was used at concentrations within the range of 10(-14) to 10(-8) M. At 10(-8) M, insulin had no effect on Na(+)-independent uptake of phosphate or on the Na(+)-dependent uptakes of methyl-alpha-D-glucopyranoside and glutamate. The onset of insulin action on phosphate uptake was detected within 15 min, and the stimulation was reversed completely within 30 min after removal of insulin from the medium. Insulin action was not blocked by protein synthesis inhibitors and was not altered by bacitracin, an inhibitor of intracellular degradation of insulin. Pretreatment with the calcium-channel blockers, nifedipine and verapamil (10(-4) M), produced significant increases in the stimulatory effect of insulin, suggesting indirectly that insulin action on phosphate uptake may be influenced by Ca2+. In contrast to in vivo studies, there was no evidence that insulin interfered with parathyroid hormone action on OK cells.

Electrophysiological Measurements of a Toad Renal Epithelial Cell Line (A6) as an Assay for Predicting Ocular Eye Irritancy

1992 ◽  
Vol 20 (2) ◽  
pp. 218-221
Author(s):  
Henning F. Bjerregaard
Keyword(s):  
Epithelial Cell ◽  
Cell Line ◽  
South African ◽  
Mdck Cells ◽  
Epithelial Cell Line ◽  
Renal Epithelial Cell ◽  
Electrophysiological Measurements ◽  
Renal Epithelial Cell Line ◽  
Darby Canine Kidney

An established epithelial cell line (A6) from a South African clawed toad (Xenopus laevis) kidney was used as a model for the corneal epithelium of the eye in order to determine ocular irritancy. When grown on Millipore filter inserts, A6 cells form a monolayer epithelium of high electrical resistance and generate a trans-epithelial potential difference. These two easily-measured electrophysiological endpoints showed a dose-related decrease after exposure for 24 hours to seven selected chemicals of different ocular irritancy potential. It was demonstrated that both trans-epithelial resistance and potential ranked closely with in vivo eye irritancy data and correlated well (r = 0.96) with loss of trans-epithelial impermeability of Madin-Darby canine kidney (MDCK) cells, detected by use of a fluorescein leakage assay.

scholarly journals Urotensin II is an Autocrine/Paracrine Growth Factor for the Porcine Renal Epithelial Cell Line, LLCPK1

Endocrinology ◽  
2003 ◽  
Vol 144 (5) ◽  
pp. 1825-1831 ◽  
Author(s):  
Mika Matsushita ◽  
Masayoshi Shichiri ◽  
Nozomi Fukai ◽  
Naoko Ozawa ◽  
Takanobu Yoshimoto ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Growth Factor ◽  
Kinase Inhibitor ◽  
Epithelial Cell Line ◽  
Urotensin Ii ◽  
Renal Epithelial Cell ◽  
Renal Epithelial Cells ◽  
Kinase C ◽  
Renal Epithelial Cell Line ◽  
Paracrine Growth Factor

Urotensin-II (UII), a cyclic dodecapeptide with potent cardiovascular effects, has recently been shown to be abundantly expressed in the human kidney and excreted in human urine. To investigate whether UII acts as an autocrine/paracrine growth factor for renal epithelial cells, we have studied the effects of human UII (hUII) on DNA synthesis, cytosolic free Ca2+ concentration ([Ca2+]i), ERK activation, and protooncogene (c-myc) expression in a porcine renal epithelial cell line (LLCPK1). hUII stimulated [3H]thymidine uptake into quiescent cells in a dose-dependent manner (10−9 to 10−7m); this effect was inhibited by a protein kinase C inhibitor (GF109203X), a MAPK kinase inhibitor (PD98059), and a calcium channel blocker (nicardipine). Neither phosphatidyl inositol-3 kinase inhibitors (LY294002, wortmannin) nor p38 kinase inhibitor (SB203580) affected the hUII-induced DNA syntheses. hUII rapidly (within 5 min) and dose-dependently (10−9 to 10−7m) increased [Ca2+]i in fura-2-loaded cells. hUII also caused a rapid and transient activation of ERK1/2 and induction of c-myc. LLCPK1 cells expressed UII mRNA and its receptor GPR14 mRNA, as determined by RT-PCR, and released UII-like immunoreactivity into media. Neutralization of endogenous UII by anti-hUII antibody, but not nonimmune serum, significantly suppressed DNA synthesis. These data suggest that hUII is an autocrine/paracrine growth factor for renal epithelial cells via activation of both protein kinase C and ERK1/2 pathways as well as Ca2+ influx via voltage-dependent Ca2+ channels.

scholarly journals Expression of phosphoenolpyruvate carboxykinase (PEPCK) chimeras in renal epithelial cells. Retention of appropriate physiological responsiveness using enhancerless retroviral vectors

1992 ◽  
Vol 284 (3) ◽  
pp. 725-732 ◽  
Author(s):  
A S Pollock ◽  
D H Lovett
Keyword(s):  
Epithelial Cell ◽  
Cyclic Amp ◽  
Cell Line ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Large Fraction ◽  
Expression System ◽  
Retroviral Vectors ◽  
Epithelial Cell Line ◽  
Renal Epithelial Cell ◽  
Renal Epithelial Cell Line

We used an enhancerless U3 mutant retroviral vector to deliver chimeras of the phosphoenolpyruvate carboxykinase (PEPCK) promoter region to a renal epithelial cell line capable of expressing PEPCK mRNA. Chimeras consisting of the PEPCK promoter and chloramphenicol acetyltransferase, neomycin phosphotransferase or human growth hormone genes were expressed after viral infection of the NRK52E renal epithelial cell line. Virus-delivered sequences in which the direction of PEPCK promoter transcription was antegrade to the normal direction of the long terminal repeat (LTR)-initiated transcription correctly upon stimulation with dexamethasone or 8-bromo cyclic AMP and upon lowering of the extracellular pH. Fluorescent primer extension in situ using primers specific for virus-delivered sequences of antegrade constructs indicated that a large fraction of NRK52E cells could be infected by co-cultivation with virus-producing psi-2 cells without G418 selection. Virus-delivered constructs whose orientation was opposite to that of the LTRs were expressed at very low levels, with transcripts detectable by PCR only in RNA from cyclic AMP-treated cells. Using reverse transcription/PCR, we demonstrated that the chimeric transcripts were from the internal PEPCK promoter rather than a functional or reconstituted Moloney LTR. PEPCK-reporter chimeras delivered by retroviral vectors demonstrated a level of expression more consistent with the level of expression of the native PEPCK gene than did transfected chimeras. This expression system should prove useful for studies of the physiological modulation of gene expression in renal tissues.

Effect of divalent heavy metals on epithelial Na+ channels in A6 cells

2007 ◽  
Vol 293 (1) ◽  
pp. F236-F244 ◽  
Author(s):  
Ling Yu ◽  
Douglas C. Eaton ◽  
My N. Helms
Keyword(s):  
Heavy Metal ◽  
Voltage Dependence ◽  
Transmembrane Domain ◽  
Single Channel ◽  
Epithelial Cell Line ◽  
Open Probability ◽  
Renal Epithelial Cell ◽  
Histidine Residues ◽  
Voltage Dependent ◽  
Renal Epithelial Cell Line

To better understand how renal Na+ reabsorption is altered by heavy metal poisoning, we examined the effects of several divalent heavy metal ions (Zn2+, Ni2+, Cu2+, Pb2+, Cd2+, and Hg2+) on the activity of single epithelial Na+ channels (ENaC) in a renal epithelial cell line (A6). None of the cations changed the single-channel conductance. However, ENaC activity [measured as the number of channels ( N) × open probability ( Po)] was decreased by Cd2+ and Hg2+ and increased by Cu2+, Zn2+, and Ni2+ but was not changed by Pb2+. Of the cations that induced an increase in Na+ channel function, Zn2+ increased N, Ni2+ increased Po, and Cu2+ increased both. The cysteine modification reagent [2-(trimethylammonium)ethyl]methanethiosulfonate bromide also increased N, whereas diethylpyrocarbonate, which covalently modifies histidine residues, affected neither Po nor N. Cu2+ increased N and stimulated Po by reducing Na+ self-inhibition. Furthermore, we observed that ENaC activity is slightly voltage dependent and that the voltage dependence of ENaC is insensitive to extracellular Na+ concentration; however, apical application of Ni2+ or diethylpyrocarbonate reduced the channel voltage dependence. Thus the voltage sensor of Xenopus ENaC is different from that of typical voltage-gated channels, since voltage appears to be sensed by histidine residues in the extracellular loops of ENaC, rather than by charged amino acids in a transmembrane domain.

Cytokine-induced release of endothelin-1 from porcine renal epithelial cell line

1990 ◽  
Vol 169 (2) ◽  
pp. 578-584 ◽  
Author(s):  
Kazuki Ohta ◽  
Yukio Hirata ◽  
Taihei Imai ◽  
Kazuo Kanno ◽  
Toshiaki Emori ◽  
...  
Keyword(s):  
Epithelial Cell ◽  
Cell Line ◽  
Epithelial Cell Line ◽  
Renal Epithelial Cell ◽  
Endothelin 1 ◽  
Renal Epithelial Cell Line
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