Microperfusion study of proximal tubule bicarbonate transport in maleic acid-induced renal tubular acidosis

1986 ◽  
Vol 250 (3) ◽  
pp. F476-F482
Author(s):  
N. Bank ◽  
H. S. Aynedjian ◽  
B. F. Mutz
Keyword(s):  
Proximal Tubule ◽  
Renal Tubular Acidosis ◽  
Maleic Acid ◽  
Basolateral Membrane ◽  
Bicarbonate Transport ◽  
Mitochondrial Energy Metabolism ◽  
Before And After ◽  
Renal Tubular ◽  
Blood Transport ◽  
Acid Administration

Microperfusion studies were carried out in rats to examine the abnormality in proximal tubule HCO3- transport caused by maleic acid administration. Permeability of the proximal tubule to HCO-3 was measured by perfusing proximal tubules with a HCO3- -free low-buffer isotonic equilibrium solution containing acetazolamide after plasma [HCO3-] had been raised by intravenous NaHCO3 infusion. Insulin recovery in the collected perfusate was approximately 100% in control and maleic acid-treated rats. CO2 influx measured by microcalorimetry was not significantly different in control vs. maleic acid-treated rats. Thus maleic acid did not cause increased permeability of the proximal tubule to either inulin or HCO3-. In a second group of experiments, proximal tubule fluid and HCO3- efflux were measured in paired-reperfusion experiments before and after maleic acid administration. The perfusion fluid contained 25 mM HCO3- and 120 mM Cl-. HCO3- absorption was inhibited 25% (79 pmol/min), Na+ was inhibited 22% (164 pmol/min), and Cl- absorption (calculated as the anion gap) by 85 pmol/min. [HCO3-] in the collected perfusate rose significantly after maleic acid, presumably accompanied by a fall in [Cl-]. The observations indicate that proximal renal tubular acidosis (RTA) induced by maleic acid is characterized by impaired lumen-to-blood transport of sodium bicarbonate and chloride but not by increased backflux. Based on previously demonstrated effects of maleic acid on mitochondrial energy metabolism and cellular ATP levels, we postulate that the principal transport abnormality is impaired basolateral membrane active sodium transport, leading to a secondary reduction in brush border Na+-H+ exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

Dysfunction of the proximal tubule underlies maleic acid-induced type II renal tubular acidosis

1982 ◽  
Vol 243 (6) ◽  
pp. F604-F611 ◽  
Author(s):  
H. A. Al-Bander ◽  
R. A. Weiss ◽  
M. H. Humphreys ◽  
R. C. Morris
Keyword(s):  
Proximal Tubule ◽  
Renal Tubular Acidosis ◽  
Maleic Acid ◽  
Free Water ◽  
Fractional Excretion ◽  
Thick Ascending Limb ◽  
Type Ii ◽  
Free Water Clearance ◽  
Plasma Bicarbonate ◽  
Renal Tubular

To investigate whether dysfunction of the proximal tubule underlies maleic acid-(MA) induced type II (“proximal”) renal tubular acidosis (RTA II), we intravenously administered either MA or acetazolamide to eight conscious trained dogs undergoing water diuresis and examined the relationship between fractional solute-free water clearance (Ch2o/GFR), a measure of NaCl reabsorption in the post-proximal nephron, and either fractional urine flow (V/GFR), a measure of total solute rejected by the proximal tubule, or the sum of fractional excretion of Cl- and Ch2o/GFR [(Ccl + Ch2o)/GFR], a measure of proximally rejected solute that is potentially reabsorbable by the thick ascending limb. When MA or acetazolamide induced brisk bicarbonaturia at normal plasma bicarbonate concentrations: 1) V/GFR, (Ccl + Ch20)GFR, and Ch2o/GFR increased strikingly; 2) at any increment of Ch2o/GFR ws not; 3) the increments of V/GFR correlated positively with those of fractional excretion of bicarbonate (P less than 0.001); 4) during hyperchloremic acidosis, MA-induced bicarbonaturia was greatly attenuated; the increment in V/GFR was halved and approximated that in Ch20/GFR, which was unchanged; 5) when plasma bicarbonate was abruptly increased, bicarbonaturia increased strikingly and V/GFR increased further but Ch20/GFR and aminoaciduria did not. We conclude that MA induces a reduction in the net rate at which the proximal tubule reabsorbs HCO-3, Na+, and Cl-. This dysfunction underlies RTA II and evokes greatly increased reabsorption of Cl- and Na+ in the post-proximal tubule.

The human NBCe1-A mutant R881C, associated with proximal renal tubular acidosis, retains function but is mistargeted in polarized renal epithelia

2006 ◽  
Vol 291 (4) ◽  
pp. C788-C801 ◽  
Author(s):  
Ashley M. Toye ◽  
Mark D. Parker ◽  
Christopher M. Daly ◽  
Jing Lu ◽  
Leila V. Virkki ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Renal Tubular Acidosis ◽  
Xenopus Oocytes ◽  
Fluorescent Protein ◽  
Basolateral Membrane ◽  
Surface Expression ◽  
Normal Activity ◽  
Proximal Renal Tubular Acidosis ◽  
Renal Tubular ◽  
The Individual

The human electrogenic renal Na-HCO3cotransporter (NBCe1-A; SLC4A4) is localized to the basolateral membrane of proximal tubule cells. Mutations in the SLC4A4 gene cause an autosomal recessive proximal renal tubular acidosis (pRTA), a disease characterized by impaired ability of the proximal tubule to reabsorb HCO3−from the glomerular filtrate. Other symptoms can include mental retardation and ocular abnormalities. Recently, a novel homozygous missense mutant (R881C) of NBCe1-A was reported from a patient with a severe pRTA phenotype. The mutant protein was described as having a lower than normal activity when expressed in Xenopus oocytes, despite having normal Na+affinity. However, without trafficking data, it is impossible to determine the molecular basis for the phenotype. In the present study, we expressed wild-type NBCe1-A (WT) and mutant NBCe1-A (R881C), tagged at the COOH terminus with enhanced green fluorescent protein (EGFP). This approach permitted semiquantification of surface expression in individual Xenopus oocytes before assay by two-electrode voltage clamp or measurements of intracellular pH. These data show that the mutation reduces the surface expression rather than the activity of the individual protein molecules. Confocal microscopy on polarized mammalian epithelial kidney cells [Madin-Darby canine kidney (MDCK)I] expressing nontagged WT or R881C demonstrates that WT is expressed at the basolateral membrane of these cells, whereas R881C is retained in the endoplasmic reticulum. In summary, the pathophysiology of pRTA caused by the R881C mutation is likely due to a deficit of NBCe1-A at the proximal tubule basolateral membrane, rather than a defect in the transport activity of individual molecules.

Studies of the urinary acidification defect induced by lithium

1982 ◽  
Vol 242 (1) ◽  
pp. F23-F29 ◽  
Author(s):  
N. Bank ◽  
P. D. Lief ◽  
H. S. Aynedjian ◽  
B. F. Mutz
Keyword(s):  
Proximal Tubule ◽  
Renal Tubular Acidosis ◽  
Electrical Potential ◽  
Distal Renal Tubular Acidosis ◽  
Distal Nephron ◽  
Luminal Membrane ◽  
Proximal Tubular ◽  
Renal Tubular ◽  
Convoluted Tubules

Experiments were carried out in rats and isolated turtle bladders to study the defect in H+ transport induced by LiCl. After 3-4 days of intraperitoneal LiCl, rats developed urinary findings of "distal" renal tubular acidosis. Proximal tubular fluid pH measured in situ by glass microelectrodes was higher in lithium-treated rats than in acidotic controls. Proximal fluid total CO2 [tCO2] was also higher, and the fraction of tCO2 leaving the proximal tubule was 14 vs. 7% (P less than 0.001). Impaired acidification was also apparent beyond distal convoluted tubules, as judged by normal distal tCO2 reabsorption but increased HCO3(-) in the urine. During NaHCO3 loading, the proximal defect was ameliorated but not the distal. Turtle bladder studies showed that mucosal lithium inhibits H+ secretion secondary to reducing transepithelial electrical potential, presumably by hyperpolarization of the luminal membrane. A similar mechanism may be responsible for lithium's effect on the distal nephron. Inhibition of proximal tubular HCO3(-) reabsorption is probably not attributable to electrical potential changes but might be due to interference of luminal membrane Na+ entry by Li+ and reduced (Na+ + Li+)-H+ exchange.

scholarly journals A mouse model for distal renal tubular acidosis reveals a previously unrecognized role of the V‐ATPase a4 subunit in the proximal tubule

2012 ◽  
Vol 4 (10) ◽  
pp. 1057-1071 ◽  
Author(s):  
J. Christopher Hennings ◽  
Nicolas Picard ◽  
Antje K. Huebner ◽  
Tobias Stauber ◽  
Hannes Maier ◽  
...  
Keyword(s):  
Mouse Model ◽  
Proximal Tubule ◽  
Renal Tubular Acidosis ◽  
Distal Renal Tubular Acidosis ◽  
Renal Tubular

Degradation mechanism of a Golgi-retained distal renal tubular acidosis mutant of the kidney anion exchanger 1 in renal cells

2014 ◽  
Vol 307 (3) ◽  
pp. C296-C307 ◽  
Author(s):  
Carmen Y. Chu ◽  
Jennifer King ◽  
Mattia Berrini ◽  
Alina C. Rumley ◽  
Pirjo M. Apaja ◽  
...  
Keyword(s):  
Quality Control ◽  
Renal Tubular Acidosis ◽  
Anion Exchanger ◽  
Mammalian Cells ◽  
Degradation Mechanism ◽  
Basolateral Membrane ◽  
Distal Renal Tubular Acidosis ◽  
Anion Exchanger 1 ◽  
Chemical Chaperone ◽  
Renal Tubular

Distal renal tubular acidosis (dRTA) can be caused by mutations in the SLC4A1 gene encoding the anion exchanger 1 (AE1). Both recessive and dominant mutations result in mistrafficking of proteins, preventing them from reaching the basolateral membrane of renal epithelial cells, where their function is needed. In this study, we show that two dRTA mutants are prematurely degraded. Therefore, we investigated the degradation pathway of the kidney AE1 G701D mutant that is retained in the Golgi. Little is known about degradation of nonnative membrane proteins from the Golgi compartments in mammalian cells. We show that the kidney AE1 G701D mutant is polyubiquitylated and degraded by the lysosome and the proteosome. This mutant reaches the plasma membrane, where it is endocytosed and degraded by the lysosome via a mechanism dependent on the peripheral quality control machinery. Furthermore, we show that the function of the mutant is rescued at the cell surface upon inhibition of the lysosome and incubation with a chemical chaperone. We conclude that modulating the peripheral quality control machinery may provide a novel therapeutic option for treatment of patients with dRTA due to a Golgi-retained mutant.

Missense mutations in Na+:HCO3− cotransporter NBC1 show abnormal trafficking in polarized kidney cells: a basis of proximal renal tubular acidosis

2005 ◽  
Vol 289 (1) ◽  
pp. F61-F71 ◽  
Author(s):  
Hong C. Li ◽  
Peter Szigligeti ◽  
Roger T. Worrell ◽  
Jeffrey B. Matthews ◽  
Laura Conforti ◽  
...  
Keyword(s):  
Renal Tubular Acidosis ◽  
Membrane Fraction ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Kidney Cells ◽  
Missense Mutations ◽  
Wild Type ◽  
Membrane Expression ◽  
Potential Recording ◽  
Renal Tubular

The kidney Na+:HCO3− cotransporter NBC1 is located exclusively on the basolateral membrane of kidney proximal tubule cells and is responsible for the reabsorption of majority of filtered bicarbonate. Two well-described missense mutations in NBC1, R510H and S427L, are associated with renal tubular acidosis (RTA). However, the exact relationship between these mutations and NBC1 dysregulation remains largely unknown. To address this question, cDNAs for wild-type kidney NBC1 and its mutants R510H and S427L were generated, fused in frame with NH2 terminally tagged GFP, and transiently expressed in Madin-Darby canine kidney cells. In parallel studies, oocytes were injected with the wild-type and mutant NBC1 cRNAs and studied for membrane expression and activity. In monolayer cells grown to polarity, the wild-type GFP-NBC1 was exclusively localized on the basolateral membrane domain. However, GFP-NBC1 mutant R510H was detected predominantly in the cytoplasm. GFP-NBC1 mutant S427L, on the other hand, was detected predominantly on the apical membrane with residual cytoplasmic retention and basolateral membrane labeling. In oocytes injected with the wild-type or mutant GFP-NBC1 cRNAs, Western blot analysis showed that wild-type NBC1 is predominantly localized in the membrane fraction, whereas NBC1-R510H mutant was predominantly expressed in the cytoplasm. NBC1-S427L mutant was mostly expressed in the membrane fraction. Functional analysis of NBC1 activity in oocytes by membrane potential recording demonstrated that compared with wild-type GFP-NBC1, the GFP-NBC1 mutants H510R and S427L exhibited significant reduction in activity. These findings suggest that the permanent isolated proximal RTA in patients with H510R or S427L mutation resulted from a combination of inactivation and mistargeting of kidney NBC1, with H510R mutant predominantly retained in the cytoplasm, whereas S427L mutant is mistargeted to the apical membrane.

Dominant-negative effect of Southeast Asian ovalocytosis anion exchanger 1 in compound heterozygous distal renal tubular acidosis

2008 ◽  
Vol 410 (2) ◽  
pp. 271-281 ◽  
Author(s):  
Saranya Kittanakom ◽  
Emmanuelle Cordat ◽  
Reinhart A. F. Reithmeier
Keyword(s):  
Cell Surface ◽  
Blood Cell ◽  
Renal Tubular Acidosis ◽  
Mdck Cells ◽  
Basolateral Membrane ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Compound Heterozygous ◽  
Intercalated Cells ◽  
Renal Tubular

The human chloride/bicarbonate AE1 (anion exchanger) is a dimeric glycoprotein expressed in the red blood cell membrane, and expressed as an N-terminal (Δ1–65) truncated form, kAE1 (kidney AE1), in the basolateral membrane of α-intercalated cells in the distal nephron. Mutations in AE1 can cause SAO (Southeast Asian ovalocytosis) or dRTA (distal renal tubular acidosis), an inherited kidney disease resulting in impaired acid secretion. The dominant SAO mutation (Δ400–408) that results in an inactive transporter and altered eythrocyte shape occurs in many dRTA families, but does not itself result in dRTA. Compound heterozygotes of four dRTA mutations (R602H, G701D, ΔV850 and A858D) with SAO exhibit dRTA and abnormal red blood cell properties. Co-expression of kAE1 and kAE1 SAO with the dRTA mutants was studied in polarized epithelial MDCK (Madin–Darby canine kidney) cells. Like SAO, the G701D and ΔV850 mutants were predominantly retained intracellularly, whereas the R602H and A858D mutants could traffic to the basolateral membrane. When co-expressed in transfected cells, kAE1 WT (wild-type) and kAE1 SAO could interact with the dRTA mutants. MDCK cells co-expressing kAE1 SAO with kAE1 WT, kAE1 R602H or kAE1 A858D showed a decrease in cell-surface expression of the co-expressed proteins. When co-expressed, kAE1 WT co-localized with the kAE1 R602H, kAE1 G701D, kAE1 ΔV850 and kAE1 A858D mutants at the basolateral membrane, whereas kAE1 SAO co-localized with kAE1 WT, kAE1 R602H, kAE1 G701D, kAE1 ΔV850 and kAE1 A858D in MDCK cells. The decrease in cell-surface expression of the dRTA mutants as a result of the interaction with kAE1 SAO would account for the impaired expression of functional kAE1 at the basolateral membrane of α-intercalated cells, resulting in dRTA in compound heterozygous patients.

Electrophysiology of basolateral bicarbonate transport in the rabbit proximal tubule

1986 ◽  
Vol 250 (2) ◽  
pp. F267-F272 ◽  
Author(s):  
B. A. Biagi ◽  
M. Sohtell
Keyword(s):  
Proximal Tubule ◽  
Basolateral Membrane ◽  
Sodium Concentration ◽  
Peak Height ◽  
Rabbit Kidney ◽  
Bicarbonate Transport ◽  
Bathing Solution ◽  
Bicarbonate Concentration ◽  
Constant Ph

Conventional microelectrodes were used to examine the electrogenic pathways for bicarbonate transport across the basolateral membranes of proximal convoluted (PCT) and straight (PST) tubule segments of the rabbit kidney perfused in vitro. When bath bicarbonate concentration was reduced from 22 to 6.6 mM at a constant pH, transient depolarizations lasting several seconds with a peak value of approximately 15 mV were seen in both tubule segments. Acetazolamide (0.1 mM) in the lumen and bath solutions reduced the magnitude and increased the duration fo this response. The final pH of the bathing solution influenced both the peak height and steady-state values of the intracellular potential when bicarbonate concentration was reduced either with constant CO2 or with an increase in CO2. Reducing bath sodium concentration by replacement with either tetramethylammonium or N-methyl-D-glucamine resulted in a sustained depolarization of both PCT and PST cells. This response was inhibited by the addition of 10(-4) M 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate (SITS) in the bathing solution. By analogy with bicarbonate transport in rat and amphibian proximal tubules, these data suggest that bicarbonate exit across the basolateral membrane of the rabbit proximal tubule is electrogenic and coupled to sodium and that basolateral bicarbonate exit can be inhibited by both acetazolamide and SITS in the bathing solution.

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