Stimulation of renal sulfate secretion by metabolic acidosis requires Na+/H+ exchange induction and carbonic anhydrase

2005 ◽  
Vol 289 (1) ◽  
pp. F208-F216 ◽  
Author(s):  
Ryan M. Pelis ◽  
Susan L. Edwards ◽  
Stan C. Kunigelis ◽  
James B. Claiborne ◽  
J. Larry Renfro
Keyword(s):  
Metabolic Acidosis ◽  
Carbonic Anhydrase ◽  
Proximal Tubule ◽  
Brush Border ◽  
Primary Cultures ◽  
Acute Effect ◽  
Renal Proximal Tubule ◽  
Ussing Chambers ◽  
Renal Tubular ◽  
Nhe Isoforms

The acute effect of metabolic acidosis on SO42− secretion by the marine teleost renal proximal tubule was examined. Metabolic acidosis was mimicked in primary cultures of winter flounder renal proximal tubule epithelium (fPTCs) mounted in Ussing chambers by reducing interstitial pH to 7.1 (normally 7.7). fPTCs with metabolic acidosis secreted SO42− at a net rate that was 40% higher than in paired isohydric controls (pH 7.7 on interstitium). The stimulation was completely blocked by the carbonic anhydrase inhibitor methazolamide (100 μM). Although Na+/H+ exchange (NHE) isoforms 1, 2, and 3 were identified in fPTCs by immunoblotting, administering EIPA (20 μM) to the interstitial and luminal bath solutions had no effect on net SO42− secretion by fPTCs with a normal interstitial pH of 7.7. However, EIPA (20 μM) blocked most of the stimulation caused by acidosis when applied to the lumen but not interstitium, demonstrating that induction of brush-border NHE activity is important. In the intact flounder, serum pH dropped 0.4 pH units (pH 7.7 to 7.3, at 2–3 h) when environmental pH was lowered from 7.8 to ∼4.3. Whereas serum [SO42−] was not altered by acidosis, renal tubular SO42− secretion rate was elevated 200%. Thus metabolic acidosis strongly stimulates renal sulfate excretion most likely by a direct effect on active renal proximal tubule SO42− secretion. This stimulation appears to be dependent on inducible brush-border NHE activity.

scholarly journals The lysosomal V-ATPase B1 subunit in proximal tubule is linked to nephropathic cystinosis

2020 ◽  
Author(s):  
Amer Jamalpoor ◽  
Albertien M van Eerde ◽  
Marc R Lilien ◽  
Charlotte AGH van Gelder ◽  
Esther A Zaal ◽  
...  
Keyword(s):  
Metabolic Acidosis ◽  
Proximal Tubule ◽  
Renal Proximal Tubule ◽  
Nephropathic Cystinosis ◽  
Renal Fanconi Syndrome ◽  
Proximal Tubule Cells ◽  
Pathogenic Variants ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells ◽  
Renal Tubular

AbstractBackgroundRecently, a 23-month-old girl presented with increased granulocyte cystine levels, metabolic acidosis and symptoms of renal Fanconi syndrome. Cystinosis was suspected and treatment with electrolytes and cysteamine, a cystine depleting agent, was started that appeared effective. However, genetic testing did not detect any variants in CTNS (the gene affected in cystinosis) but instead revealed pathogenic variants in ATP6V1B1. ATP6V1B1 encodes the B1 subunit of the vacuolar H+-ATPase (V-ATPase), that is linked to autosomal recessive distal renal tubular acidosis, a metabolic disorder with an inappropriately alkaline urine and deafness. Here, the unknown link between ATP6V1B1 gene deficiency and proximal tubulopathy as well as a possible link to cystinosis pathophysiology was investigated.MethodsWe used CRISPR/Cas9 technology to selectively knockout the ATP6V1B1 or CTNS gene in human renal proximal tubule cells and compare their proteomic and metabolomic profile with isogenic wild type proximal tubule cells.ResultsATP6V1B1 was expressed along the human distal but also the proximal segments of the nephron. Consistent with the clinical data, loss of ATP6V1B1 in renal proximal tubule cells resulted in increased cystine levels with autophagy activation. Further, omics profiling showed that both ATP6V1B1-/- and CTNS-/- cells are in metabolic acidosis with impaired autophagy and signs of proximal tubular epithelial dysfunction.ConclusionWe identified the lysosomal V-ATPase B1 subunit to play an important role in proximal tubule function, regulating cystine transport and autophagy in human renal proximal tubule cells through its interaction with cystinosin and mTOR-signaling.

Transepithelial sulfate transport by avian renal proximal tubule epithelium in primary culture

2002 ◽  
Vol 283 (6) ◽  
pp. R1354-R1361 ◽  
Author(s):  
Paul L. Dudas ◽  
J. Larry Renfro
Keyword(s):  
Proximal Tubule ◽  
Primary Cultures ◽  
Renal Proximal Tubule ◽  
Proximal Tubules ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Electrophysiological Properties ◽  
Ussing Chambers ◽  
And Control ◽  
Inorganic Sulfate

The mechanisms and control of transepithelial inorganic sulfate (Si) transport by primary cultures of chick renal proximal tubule monolayers in Ussing chambers were determined. The competitive anion, S2O3 2− (5 mM), reduced both unidirectional reabsorptive and secretory fluxes and net Sireabsorption with no effect on electrophysiological properties. The carbonic anhydrase (CA) inhibitor ethoxzolamide decreased net Si reabsorption ∼45%. CAII protein and activity were detected in isolated chick proximal tubules by immunoblots and biochemical assay, respectively. Cortisol reduced net Sireabsorption up to ∼50% in a concentration-dependent manner. Thyroid hormone increased net Si reabsorption threefold in 24 h, and parathyroid hormone (PTH) acutely stimulated net Sireabsorption ∼45%. These data indicate that CA participates in avian proximal tubule active transepithelial Si reabsorption, which cortisol directly inhibits and T3 and PTH directly stimulate.

Control of phosphate transport in flounder renal proximal tubule primary cultures

1989 ◽  
Vol 256 (4) ◽  
pp. R850-R857 ◽  
Author(s):  
A. Gupta ◽  
J. L. Renfro
Keyword(s):  
Proximal Tubule ◽  
Primary Cultures ◽  
Phosphate Transport ◽  
Renal Proximal Tubule ◽  
Pseudopleuronectes Americanus ◽  
Ussing Chambers ◽  
Long Latency ◽  
Phosphate Availability ◽  
Phosphate Fluxes ◽  
Renal Proximal Tubule Cells

Unidirectional mucosal-to-serosal (Jm----s) and serosal-to-mucosal (Js----m) transepithelial phosphate fluxes across monolayers of flounder (Pseudopleuronectes americanus) renal proximal tubule cells in primary culture were examined for effects of diacylglycerols, phorbol ester, A23187, forskolin, and extracellular phosphate availability. Tissues were cultured on floating collagen rafts and studied short circuited in Ussing chambers. Transepithelial electrical properties were continuously monitored and were unaffected by any of the treatments compared with paired controls. Under usual conditions (phosphate = 0.4 mM) tissues invariably displayed net phosphate reabsorption [Js----m = 2.3 +/- 0.52; Jm----a = 7.1 +/- 1.77; Jnet = 4.9 +/- 1.45 (SE) nmol.cm-2.h-1]. Acute elevation of bath phosphate concentration above 0.5 mM stimulated net secretion. Exposure to 100 microM 1,2-dihexanoyl-sn-glycerol stimulated net phosphate secretion within 30 min, the result of a fivefold increase in Js----m. Phorbol-12,13-didecanoate stimulated net phosphate secretion by increasing Js----m and decreasing Jm----s. The inactive diacylglycerol, 1,3-didecanoyl-rac-glycerol (100 microM), had no effect on phosphate fluxes. A23187 stimulated net phosphate secretion; Jm----s was reduced almost fourfold while Js----m was increased threefold. Forskolin (10 microM) stimulated net reabsorption more than threefold after a long latency (2 h). These data indicate that renal phosphate secretion and reabsorption may be regulated by several putative intracellular messengers. In addition, extracellular phosphate availability may modulate renal phosphate handling.

Mitochondrial aquaporin-8 in renal proximal tubule cells: evidence for a role in the response to metabolic acidosis

2012 ◽  
Vol 303 (3) ◽  
pp. F458-F466 ◽  
Author(s):  
Sara M. Molinas ◽  
Laura Trumper ◽  
Raúl A. Marinelli
Keyword(s):  
Metabolic Acidosis ◽  
Protein Expression ◽  
Proximal Tubule ◽  
Ammonia Excretion ◽  
Renal Proximal Tubule ◽  
In Vivo Studies ◽  
Proximal Tubule Cell ◽  
Inner Mitochondrial Membrane ◽  
Ammonia Transport ◽  
In Cells

Mitochondrial ammonia synthesis in proximal tubules and its urinary excretion are key components of the renal response to maintain acid-base balance during metabolic acidosis. Since aquaporin-8 (AQP8) facilitates transport of ammonia and is localized in inner mitochondrial membrane (IMM) of renal proximal cells, we hypothesized that AQP8-facilitated mitochondrial ammonia transport in these cells plays a role in the response to acidosis. We evaluated whether mitochondrial AQP8 (mtAQP8) knockdown by RNA interference is able to impair ammonia excretion in the human renal proximal tubule cell line, HK-2. By RT-PCR and immunoblotting, we found that AQP8 is expressed in these cells and is localized in IMM. HK-2 cells were transfected with short-interfering RNA targeting human AQP8. After 48 h, the levels of mtAQP8 protein decreased by 53% ( P < 0.05). mtAQP8 knockdown decreased the rate of ammonia released into culture medium in cells grown at pH 7.4 (−31%, P < 0.05) as well as in cells exposed to acid (−90%, P < 0.05). We also evaluated mtAQP8 protein expression in HK-2 cells exposed to acidic medium. After 48 h, upregulation of mtAQP8 (+74%, P < 0.05) was observed, together with higher ammonia excretion rate (+73%, P < 0.05). In vivo studies in NH4Cl-loaded rats showed that mtAQP8 protein expression was also upregulated after 7 days of acidosis in renal cortex (+51%, P < 0.05). These data suggest that mtAQP8 plays an important role in the adaptive response of proximal tubule to acidosis possibly facilitating mitochondrial ammonia transport.

Primary cultures of renal proximal tubule cells derived from individuals with primary hyperoxaluria

2009 ◽  
Vol 37 (3) ◽  
pp. 127-132 ◽  
Author(s):  
Karen L. Price ◽  
Sally-Anne Hulton ◽  
William G. van’t Hoff ◽  
John R. Masters ◽  
Gill Rumsby
Keyword(s):  
Proximal Tubule ◽  
Primary Cultures ◽  
Primary Hyperoxaluria ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells

scholarly journals Impaired Na+−K+-ATPase signaling in renal proximal tubule contributes to hyperuricemia-induced renal tubular injury

2018 ◽  
Vol 50 (3) ◽  
pp. e452-e452 ◽  
Author(s):  
Jing Xiao ◽  
Xiaoli Zhang ◽  
Chensheng Fu ◽  
Qingmei Yang ◽  
Ying Xie ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Renal Proximal Tubule ◽  
Tubular Injury ◽  
Renal Tubular

Renal organic anion secretion: evidence for dopaminergic and adrenergic regulation

1996 ◽  
Vol 271 (5) ◽  
pp. R1372-R1379 ◽  
Author(s):  
P. A. Halpin ◽  
J. L. Renfro
Keyword(s):  
Proximal Tubule ◽  
Organic Anion ◽  
Primary Cultures ◽  
Regulatory Control ◽  
Dichlorophenoxyacetic Acid ◽  
Adrenergic Stimulation ◽  
Anion Secretion ◽  
Ussing Chambers ◽  
2,4 Dichlorophenoxyacetic Acid ◽  
Organic Anion Secretion

To examine possible regulatory control of renal proximal tubule organic anion secretion, winter flounder (Pleuronectes americanus) proximal tubule primary cultures were mounted in Ussing chambers. Unidirectional fluxes of [2,4-(14)C]dichlorophenoxyacetic acid were determined under short-circuited conditions. Phorbol 12-myristate 13-acetate (1 microM) caused a significant (P < 0.01) inhibition of net 2,4-dichlorophenoxyacetic acid secretion. Preincubation with staurosporine (1 microM) blocked the phorbol 12-myristate 13-acetate-induced decrease in secretion. Neither forskolin (10 microM) nor W-7 (20 microM) had any effect on net transport. Elevation of intracellular calcium activity with either A-23187 or thapsigargin produced a slight, transient decrease in transport. Addition of dopamine (1 microM) to the peritubular side, but not the luminal side, caused a significant (P < 0.01) decrease in net secretion. Both the alpha-adrenergic agonist oxymetazoline (10 microM) and depletion of intracellular Na+ transiently, but significantly (P < 0.05), increased net transport. The data indicate that renal organic anion excretion may be regulated through dopaminergic inhibition and alpha-adrenergic stimulation of net transepithelial secretion.

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