Mechanisms of Transcellular C1-Transport in Mammalian Renal Proximal Tubules

Physiology ◽  
1989 ◽  
Vol 4 (1) ◽  
pp. 18-22
Author(s):  
S Sasaki ◽  
F Marumo
Keyword(s):  
Proximal Tubule ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Renal Proximal Tubule ◽  
Proximal Tubules ◽  
Significant Fraction ◽  
Base Exchange ◽  
Renal Proximal Tubules

In mammalian renal proximal tubule, a significant fraction of Cl- reabsorption passes through the cell by electroneutral mechanisms. At the apical membrane, Cl- is taken up into the cell by a Cl--base exchange, and it appears to exit the basolateral membrane through K+-Cl- cotransport and Na+-HCO3--Cl- exchange.

scholarly journals Tandem Requirement for Full Renal D1R and D5R Activity

2019 ◽  
Author(s):  
Selim Rozyyev ◽  
Annabelle P. Crusan ◽  
Andrew C. Tiu ◽  
Julie A. Jurgens ◽  
Justin Michael B. Quion ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Structural Features ◽  
Renal Proximal Tubule ◽  
Proximal Tubules ◽  
Proximal Tubule Cells ◽  
Renal Proximal Tubules ◽  
Genetic Ablation ◽  
R And D ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells

ABSTRACTThe peripheral dopaminergic system promotes the maintenance of blood pressure homeostasis by engendering natriuresis, mainly through the renal D1R and D5R receptors. This effect is most apparent under conditions of moderate body sodium excess. Human and rodent renal proximal tubules express both receptors, which share common structural features and pharmacological profiles. Genetic ablation of either receptor in the kidney results in hypertension in mice. In this study, we demonstrated that in renal proximal tubules, these two receptors colocalized, co-immunoprecipitated, co-segregated in lipid rafts, and heterodimerized with one another, which was enhanced by treatment with the D1R/D5R agonist fenoldopam (1 μM, 30 min). Gene silencing via antisense oligonucleotides in renal proximal tubule cells abrogated cAMP production and sodium transport in response to fenoldopam. Our results highlight the cooperation and co-dependence of these two receptors through heterodimerization in renal proximal tubule cells.

Renal and intestinal transport defects in Slc26a6-null mice

2005 ◽  
Vol 288 (4) ◽  
pp. C957-C965 ◽  
Author(s):  
Zhaohui Wang ◽  
Tong Wang ◽  
Snezana Petrovic ◽  
Biguang Tuo ◽  
Brigitte Riederer ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Apical Membrane ◽  
Statistical Significance ◽  
Proximal Tubules ◽  
Wild Type ◽  
Base Exchange ◽  
Ussing Chambers ◽  
Baseline Rate ◽  
Kidney Proximal Tubule ◽  
Stimulation Of

SLC26A6 (PAT1, CFEX) is an anion exchanger that is expressed on the apical membrane of the kidney proximal tubule and the small intestine. Modes of transport mediated by SLC26A6 include Cl−/formate exchange, Cl−/HCO3− exchange, and Cl−/oxalate exchange. To study its role in kidney and intestinal physiology, gene targeting was used to prepare mice lacking Slc26a6. Homozygous mutant Slc26a6−/− mice appeared healthy and exhibited a normal blood pressure, kidney function, and plasma electrolyte profile. In proximal tubules microperfused with a low-HCO3−/high-Cl− solution, the baseline rate of fluid absorption ( Jv), an index of NaCl transport under these conditions, was the same in wild-type and null mice. However, the stimulation of Jv by oxalate observed in wild-type mice was completely abolished in Slc26a6-null mice ( P < 0.05). Formate stimulation of Jv was partially reduced in null mice, but the difference from the response in wild-type mice did not reach statistical significance. Apical membrane Cl−/base exchange activity, assayed with the pH-sensitive dye BCPCF in microperfused proximal tubules, was decreased by 58% in Slc26a6−/− animals ( P < 0.001 vs. wild types). In the duodenum, the baseline rate of HCO3− secretion measured in mucosal tissue mounted in Ussing chambers was decreased by ∼30% ( P < 0.03), whereas the forskolin-stimulated component of HCO3− secretion was the same in wild-type and Slc26a6−/− mice. We conclude that Slc26a6 mediates oxalate-stimulated NaCl absorption, contributes to apical membrane Cl−/base exchange in the kidney proximal tubule, and also plays an important role in HCO3− secretion in the duodenum.

scholarly journals Neonatal rabbit proximal tubule basolateral membrane Na+/H+antiporter and Cl−/base exchange

1999 ◽  
Vol 276 (6) ◽  
pp. R1792-R1797 ◽  
Author(s):  
Mehul Shah ◽  
Raymond Quigley ◽  
Michel Baum
Keyword(s):  
Proximal Tubule ◽  
Intracellular Ph ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Fluorescent Dye ◽  
Adult Rabbit ◽  
Base Exchange ◽  
Straight Tubules ◽  
Exchange Activity

The present in vitro microperfusion study examined the maturation of Na+/H+antiporter and Cl−/base exchanger on the basolateral membrane of rabbit superficial proximal straight tubules (PST). Intracellular pH (pHi) was measured with the pH-sensitive fluorescent dye 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein in neonatal and adult superficial PST. Na+/H+antiporter activity was examined after basolateral Na+ addition in tubules initially perfused and bathed without Na+. Neonatal Na+/H+antiporter activity was ∼40% that of adult segment (9.7 ± 1.5 vs. 23.7 ± 3.2 pmol ⋅ mm−1 ⋅ min−1; P < 0.001). The effect of bath Cl− removal on pHi was used to assess the rates of basolateral Cl−/base exchange. In both neonatal and adult PST, the Cl−/base exchange activity was significantly higher in the presence of 25 mM[Formula: see text] than in the absence of[Formula: see text] and was inhibited by cyanide and acetazolamide, consistent with Cl−/[Formula: see text]exchange. The proton flux rates in the presence of bicarbonate in neonatal and adult tubules were 14.1 ± 3.6 and 19.5 ± 3.5 pmol ⋅ mm−1min−1, respectively ( P = NS), consistent with a mature rate of Cl−/[Formula: see text]exchanger activity in neonatal tubules. Basolateral Cl−/base exchange activity in the absence of CO2 and[Formula: see text], with luminal and bath cyanide and acetazolamide, was greater in adult than in neonatal PST and inhibited by bath DIDS consistent with a maturational increase in Cl−/OH−exchange. We have previously shown that the rates of the apical membrane Na+/H+antiporter and Cl−/base exchanger were approximately fivefold lower in neonatal compared with adult rabbit superficial PST. These data demonstrate that neonatal PST basolateral membrane Na+/H+antiporter and Cl−/base exchanger activities are relatively more mature than the Na+/H+antiporter and Cl−/base exchangers on the apical membrane.

scholarly journals An androgen-inducible proximal tubule-specific Cre recombinase transgenic model

2008 ◽  
Vol 294 (6) ◽  
pp. F1481-F1486 ◽  
Author(s):  
Huiping Li ◽  
Xiyou Zhou ◽  
Deborah R. Davis ◽  
Di Xu ◽  
Curt D. Sigmund
Keyword(s):  
Transgenic Mice ◽  
Proximal Tubule ◽  
Cre Recombinase ◽  
Renal Proximal Tubule ◽  
Proximal Tubules ◽  
Renal Proximal Tubules ◽  
Female Mice ◽  
Cell Specificity ◽  
Reporter Mice ◽  
Transgenic Mouse Strain

To facilitate the study of renal proximal tubules, we generated a transgenic mouse strain expressing an improved Cre recombinase (iCre) under the control of the kidney androgen-regulated protein (KAP) promoter. The transgene was expressed in the kidney of male mice but not in female mice. Treatment of female transgenic mice with androgen induced robust expression of the transgene in the kidney. We confirmed the presence of Cre recombinase activity and the cell specificity by breeding the KAP2-iCRE mice with ROSA26 reporter mice. X-Gal staining of kidney sections from male double transgenic mice showed robust staining in the epithelial cells of renal proximal tubules. β-Gal staining in female mice became evident in proximal tubules after administration of androgen. This model of inducible Cre recombinase in the renal proximal tubule should provide a novel useful tool for studying the physiological significance of genes expressed in the renal proximal tubule. This has advantages over other current models where Cre recombinase expression is constitutive, not inducible.

scholarly journals Electro-osmosis and the reabsorption of fluid in renal proximal tubules.

1985 ◽  
Vol 85 (5) ◽  
pp. 699-728 ◽  
Author(s):  
S McLaughlin ◽  
R T Mathias
Keyword(s):  
Electric Field ◽  
Proximal Tubule ◽  
Fluid Transport ◽  
Fluid Velocity ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Proximal Tubules ◽  
Renal Proximal Tubules ◽  
Sodium Pumps ◽  
Electro Osmosis

The lateral intercellular spaces (LIS) are believed to be the final common pathway for fluid reabsorption from the renal proximal tubule. We postulate that electrogenic sodium pumps in the lateral membranes produce an electrical potential within the LIS, that the lateral membranes bear a net negative charge, and that fluid moves parallel to these membranes because of Helmholtz-type electro-osmosis, the field-induced movement of fluid adjacent to a charged surface. Our theoretical analysis indicates that the sodium pumps produce a longitudinal electric field of the order of 1 V/cm in the LIS. Our experimental measurements demonstrate that the electrophoretic mobility of rat renal basolateral membrane vesicles is 1 micron/s per V/cm, which is also the electro-osmotic fluid velocity in the LIS produced by a unit electric field. Thus, the fluid velocity in the LIS due to electro-osmosis should be of the order of 1 micron/s, which is sufficient to account for the observed reabsorption of fluid from renal proximal tubules. Several experimentally testable predictions emerge from our model. First, the pressure in the LIS need not increase when fluid is transported. Thus, the LIS of mammalian proximal tubules need not swell during fluid transport, a prediction consistent with the observations of Burg and Grantham (1971, Membranes and Ion Transport, pp. 49-77). Second, the reabsorption of fluid is predicted to cease when the lumen is clamped to a negative voltage. Our analysis predicts that a voltage of -15 mV will cause fluid to be secreted into the Necturus proximal tubule, a prediction consistent with the observations of Spring and Paganelli (1972, J. Gen. Physiol., 60:181).

Luminal flow rate regulates proximal tubule H-HCO3 transporters

1992 ◽  
Vol 262 (1) ◽  
pp. F47-F54 ◽  
Author(s):  
P. A. Preisig
Keyword(s):  
Proximal Tubule ◽  
Flow Rate ◽  
Initial Rate ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Rate Dependence ◽  
Unstirred Layer ◽  
Disulfonic Acid ◽  
Luminal Flow

In vivo microperfusion was used to examine the mechanism of luminal flow rate dependence of proximal tubule acidification. Luminal flow rate was acutely changed between 5 and 40 nl/min, while luminal and peritubular capillary composition were held constant. With inhibition of basolateral membrane base transport by peritubular 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), cell pH (pHi) provides a sensitive index of apical membrane H secretory activity. At a luminal perfusate [HCO3] of 25 mM, progressive increases in luminal flow rate (5----15----25----40 nl/min) caused progressive increases in pHi. This effect was of a smaller magnitude with a luminal perfusate [HCO3] of 60 mM and was further decreased at a luminal perfusate [HCO3] of 100 mM. This pattern of diminished flow rate dependence at higher luminal [HCO3] is consistent with the presence of a luminal unstirred layer, whose composition can be modified by luminal flow rate. The activity of the apical membrane Na-H antiporter, assayed as the initial rate of pHi recovery from an acid load in the presence of peritubular DIDS, was faster at 40 compared with 5 nl/min. Basolateral membrane Na-3HCO3 symporter activity, assayed as the initial rate of pHi recovery from an alkali load in the absence of luminal and peritubular chloride, was faster at 40 compared with 5 nl/min. This effect was eliminated by luminal amiloride, suggesting an indirect effect of flow mediated by changes in pHi secondary to flow rate-dependent changes in apical membrane Na-H antiporter activity. In summary, increases in luminal flow rate directly increase apical membrane H secretion, possibly by modification of a luminal unstirred layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of an apical \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{Cl}^{-}{/}\mathrm{HCO}_{3}^{-}\) \end{document} exchanger in rat kidney proximal tubule

2003 ◽  
Vol 285 (3) ◽  
pp. C608-C617 ◽  
Author(s):  
Snezana Petrovic ◽  
Liyun Ma ◽  
Zhaohui Wang ◽  
Manoocher Soleimani
Keyword(s):  
Proximal Tubule ◽  
Apical Membrane ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Immunocytochemical Staining ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Kidney Proximal Tubule ◽  
Anion Transporter

SLC26A6 (or putative anion transporter 1, PAT1) is located on the apical membrane of mouse kidney proximal tubule and mediates [Formula: see text] exchange in in vitro expression systems. We hypothesized that PAT1 along with a [Formula: see text] exchange is present in apical membranes of rat kidney proximal tubules. Northern hybridizations indicated the exclusive expression of SLC26A6 (PAT1 or CFEX) in rat kidney cortex, and immunocytochemical staining localized SLC26A6 on the apical membrane of proximal tubules, with complete prevention of the labeling with the preadsorbed serum. To examine the functional presence of apical [Formula: see text] exchanger, proximal tubules were isolated, microperfused, loaded with the pH-sensitive dye BCPCF-AM, and examined by digital ratiometric imaging. The pH of the perfusate and bath was kept at 7.4. Buffering capacity was measured, and transport rates were calculated as equivalent base flux. The results showed that in the presence of basolateral DIDS (to inhibit [Formula: see text] cotransporter 1) and apical EIPA (to inhibit Na+/H+ exchanger 3), the magnitude of cell acidification in response to addition of luminal Cl– was ∼5.0-fold higher in the presence than in the absence of [Formula: see text]. The Cl–-dependent base transport was inhibited by ∼61% in the presence of 0.5 mM luminal DIDS. The presence of physiological concentrations of oxalate in the lumen (200 μM) did not affect the [Formula: see text] exchange activity. These results are consistent with the presence of SLC26A6 (PAT1) and [Formula: see text] exchanger activity in the apical membrane of rat kidney proximal tubule. We propose that SLC26A6 is likely responsible for the apical [Formula: see text] (and Cl–/OH–) exchanger activities in kidney proximal tubule.

Electrophysiological evidence for Cl secretion in shark renal proximal tubules

1985 ◽  
Vol 248 (2) ◽  
pp. F282-F295 ◽  
Author(s):  
K. W. Beyenbach ◽  
E. Fromter
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Proximal Tubules ◽  
In Vitro Perfusion ◽  
Electrophysiological Properties ◽  
Electrophysiological Responses ◽  
Tubule Lumen ◽  
Transepithelial Voltage ◽  
Cl Conductance

The electrophysiology of shark proximal tubules (Squalus acanthias) was investigated using conventional microelectrodes and cable analysis. Under in vitro perfusion with symmetrical Ringer solutions, tubule transepithelial resistance was 36.3 +/- 2.3 omega X cm2 (means +/- SE, n = 44). Other electrophysiological variables varied widely under control conditions. In unstimulated tubules (n = 16) the transepithelial voltage (VT,o) was lumen positive (1.2 +/- 0.2 mV), the basolateral membrane potential (Vbl,x) was -61.3 +/- 1.6 mV, and the fractional resistance of the apical membrane (fRa) was 0.67 +/- 0.02. Spontaneously stimulated tubules (n = 28) had lumen-negative VT,o values (-1.5 +/- 0.4 mV), low Vbl,x values (-41.3 +/- 1.7 mV), and low fRa values (0.30 +/- 0.02). The stimulated state can be induced in unstimulated tubules via treatment with cAMP. Multiple microelectrode impalements in a single tubule revealed epithelial cells sharing similar electrophysiological properties. Selective ion substitutions in the tubule lumen and peritubular bath uncovered an increased Cl conductance in the apical membrane of spontaneously and cAMP-stimulated tubules. Anthracene-9-carboxylic acid tended to reverse the stimulated state, and furosemide hyperpolarized Vbl,x. These results constitute the first evidence for secretory Cl transport in a renal proximal tubule. The electrophysiological responses to ion substitutions, stimulators, and inhibitors are strikingly similar to those of known Cl-transporting epithelia.

Daunomycin secretion by killfish renal proximal tubules

1995 ◽  
Vol 269 (2) ◽  
pp. R370-R379 ◽  
Author(s):  
D. S. Miller
Keyword(s):  
Organic Cation ◽  
Basolateral Membrane ◽  
Organic Cation Transporter ◽  
Proximal Tubules ◽  
Epifluorescence Microscopy ◽  
Buffer Solution ◽  
Simple Diffusion ◽  
Renal Proximal Tubules ◽  
Cellular Accumulation ◽  
Tubular Lumen

Epifluorescence microscopy and video-image analysis were used to measure the uptake of the fluorescent anthracycline daunomycin by intact killifish renal proximal tubules. When tubules were incubated in medium containing 2-5 microM daunomycin, the drug accumulated in the cells and the tubular lumen. At steady state, luminal fluorescence was two to three times greater than cellular fluorescence. Luminal accumulation of daunomycin was reduced when tubules were exposed to the multidrug-resistance (MDR) transporter modifiers verapamil and cyclosporin A (CSA), but not tetraethylammonium (TEA), a model substrate for the renal organic cation transport system. NaCN and vanadate reduced luminal drug accumulation. In contrast, cellular daunomycin accumulation was not affected by verapamil, CSA, TEA, or vanadate and was only slightly reduced by NaCN. When the pH of the buffer solution was decreased from 8.25 to 7.25, luminal, but not cellular, accumulation of daunomycin was again reduced by CSA; however, TEA now reduced cellular and luminal accumulation. These findings are consistent with daunomycin being actively secreted in killifish proximal tubule by two mechanisms. At pH 8.25, daunomycin crossed the basolateral membrane by simple diffusion and was secreted into the tubular lumen by the MDR transporter. At pH 7.25, daunomycin was transported across the basolateral membrane by simple diffusion and carrier-mediated uptake on the organic cation transporter and was secreted into the lumen by the MDR transporter and the organic cation/H+ exchanger.

Interaction of the metal chelator DMPS with OAT1 and OAT3 in intact isolated rabbit renal proximal tubules

2004 ◽  
Vol 286 (1) ◽  
pp. F68-F76 ◽  
Author(s):  
A. Lungkaphin ◽  
V. Chatsudthipong ◽  
K. K. Evans ◽  
C. E. Groves ◽  
S. H. Wright ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Urinary Excretion ◽  
Basolateral Membrane ◽  
Proximal Tubules ◽  
Bathing Medium ◽  
Renal Proximal Tubules ◽  
Estrone Sulfate ◽  
Metal Chelator ◽  
Prevalent Form

2,3-Dimercapto-1-propanesulfonic acid (DMPS) is used clinically to increase urinary excretion of heavy metals, including mercury and arsenic. We used single S2 segments and suspensions of rabbit renal proximal tubules (RPT) to test the interaction of this anionic heavy metal chelator with basolateral transporters OAT1 and OAT3. RTPCR revealed expression of both transporters in single S2 segments. [3H]PAH and 3H-labeled estrone sulfate ([3H]ES) were used as specific substrates for rbOAT1 and rbOAT3, respectively. PAH and ES were transported into nonperfused single RPT segments with Kt values of 67 ± 20 and 3.4 ± 1.2 μM, respectively, and into tubule suspensions with Kt values of 58 ± 17 and 7.7 ± 2.1 μM, respectively. Reduced DMPS (DMPSH) inhibited uptake of both substrates into single tubule segments with Kapp values of 405 ± 49 μM (for [3H]PAH) and 320 ± 66 μM (for [3H]ES). Oxidized DMPS (DMPSS), the prevalent form in the blood, also inhibited uptakes of [3H]PAH ( Kapp of 766 ± 190 μM) and [3H]ES (696 ± 166 μM). Inward gradients of ES, DMPSH, and DMPSS trans-stimulated the 30-s efflux of preloaded [3H]ES across the basolateral membrane of RPT. Similarly, DMPSH, and PAH itself, trans-stimulated the 15-s efflux of [3H]PAH. In contrast, efflux of [3H]PAH was inhibited by the presence of DMPSS in the bathing medium. These data suggest that, whereas both OAT1 and OAT3 probably transport DMPSH, DMPSS transport may be limited to OAT3. This is the first evidence showing that both OAT1 and OAT3 can transport DMPS across the basolateral membrane of RPT.

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