Expression of an Artificial Cl? Channel in Microperfused Renal Proximal Tubules

Matsumoto, Natsuki; Tsuruoka, Shuichi; Iwamoto, Takeo; Tomich, John M.; Ito, Katsuhiko; Imai, Masashi

doi:10.1007/s00232-003-2018-8

Cited by 3 publications

(3 citation statements)

References 17 publications

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“…J Na , J Cl , and J v were measured in the isolated perfused proximal tubules using standard techniques (31). The luminal flow rate was adjusted to 8-9 nL/min by regulating the hydrostatic perfusion pressure.…”

Section: Methodsmentioning

confidence: 99%

Claudin-2–deficient mice are defective in the leaky and cation-selective paracellular permeability properties of renal proximal tubules

Muto¹,

Hara

Taniguchi³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

263

236

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Claudin-2 is highly expressed in tight junctions of mouse renal proximal tubules, which possess a leaky epithelium whose unique permeability properties underlie their high rate of NaCl reabsorption. To investigate the role of claudin-2 in paracellular NaCl transport in this nephron segment, we generated knockout mice lacking claudin-2 (Cldn2 −/− ). The Cldn2 −/− mice displayed normal appearance, activity, growth, and behavior. Light microscopy revealed no gross histological abnormalities in the Cldn2 −/− kidney. Ultrathin section and freezefracture replica electron microscopy revealed that, similar to those of wild types, the proximal tubules of Cldn2 −/− mice were characterized by poorly developed tight junctions with one or two continuous tight junction strands. In contrast, studies in isolated, perfused S2 segments of proximal tubules showed that net transepithelial reabsorption of Na + , Cl -, and water was significantly decreased in Cldn2 −/− mice and that there was an increase in paracellular shunt resistance without affecting the apical or basolateral membrane resistances. Moreover, deletion of claudin-2 caused a loss of cation (Na + ) selectivity and therefore relative anion (Cl -) selectivity in the proximal tubule paracellular pathway. With free access to water and food, fractional Na + and Cl -excretions in Cldn2 −/− mice were similar to those in wild types, but both were greater in Cldn2 −/− mice after i.v. administration of 2% NaCl. We conclude that claudin-2 constitutes leaky and cation (Na + )-selective paracellular channels within tight junctions of mouse proximal tubules. mouse proximal tubule | tight junction | paracellular transport | Na/Cl transport | water transport T ight junctions (TJs) are circumferential seals around cells that selectively modulate paracellular permeability between extracellular compartments (1-3). On ultrathin-section electron microscopy, TJs appear as foci where the plasma membranes of neighboring cells make complete contact (4). On freeze-fracture electron microscopy, TJs appear as a continuous and anastomosing network of intramembranous particle strands (TJ strands) (5). These strands are mainly composed of linearly polymerized integral membrane proteins called claudins with molecular masses of ∼23 kDa (2, 3, 6). The claudin gene family contains more than 20 members in humans and in mice (2, 3, 7). The expression pattern of claudins varies considerably; most cell types express more than two claudins in various combinations to constitute mosaic TJ strands.Through the formation of TJ strands, claudins are directly involved in creating a primary barrier to the paracellular diffusion of solutes and water across epithelia (8). However, TJs are not a simple barrier: the barrier varies in tightness, measured by the transepithelial electrical resistance (R T ), and charge selectivity. Furuse et al. (9) reported that, when canine claudin-2 cDNA was transfected into high-resistance Madin-Darby canine kidney (MDCK) I cells primarily expressing claudins-1 and -4, the R T decreas...

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Section: Methodsmentioning

confidence: 99%

Claudin-2–deficient mice are defective in the leaky and cation-selective paracellular permeability properties of renal proximal tubules

Muto¹,

Hara

Taniguchi³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

263

236

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“…Net transepithelial water flux (J V , nl/mm/min) was calculated as J V = V o (C* o /C* i – 1)/L, where V o is the fluid collected rate (nl/min), L is the tubular length (mm), C* o and C* i are concentrations of 14 C-methoxy inulin (New England Nuclear, Boston, Mass., USA) of the collected fluid and the luminal perfusate, respectively [16, 17]. The values of J V greater than ± 0.1 nl/mm/min were assumed to represent water movement, including mechanical leaks, and were discarded.…”

Section: Methodsmentioning

confidence: 99%

“…The values of J V greater than ± 0.1 nl/mm/min were assumed to represent water movement, including mechanical leaks, and were discarded. Net transepithelial fluxes of Na + and K + were determined by measuring concentrations of the luminal perfusate and collected fluid with a continuous flow fluorometer (Nanoflo; W-P Instruments) [17] and an ultramicro flame photometer (AFA-707-D; APEL, Saitama, Japan) [16], respectively. The net transepithelial fluxes of the solute X (J X , pEq/mm/min) were calculated according to the equation: J X = ([X] i – [X] o ) V o /L, where [X] i and [X] o are concentrations of the solute X in the luminal perfusate and the collected fluid, respectively.…”

Section: Methodsmentioning

confidence: 99%

Effect of Trimethoprim-Sulfamethoxazole on Na<sup>+</sup> and K<sup>+</sup> Transport Properties in the Rabbit Cortical Collecting Duct Perfused in vitro

et al. 2006

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Background: In this study, the membrane mechanisms of hyperkalemia caused by trimethoprim-sulfamethoxazole (TMP-SMX) combination antibiotics were assessed in the cortical collecting duct (CCD). Methods: We used the microelectrode technique and flux measurements, and examined the effects of TMP and SMX on electrical properties of the apical and basolateral membranes in the rabbit CCD perfused in vitro. Results: TMP in the lumen caused increases in apical membrane voltage, fractional apical membrane resistance (fR_A), and transepithelial resistance (R_T), all effects which were completely inhibited by luminal amiloride, but not by luminal Ba²⁺. The luminal TMP inhibited both net Na⁺ reabsorption and K⁺ secretion in the CCD. TMP in the bath slightly but significantly depolarized transepithelial voltage and basolateral membrane voltage without influencing fR_A or R_T. SMX in the lumen or bath had no effect on barrier voltages or resistances. Conclusion: TMP mainly acts on the apical membrane of the CCD, inhibits the amiloride-sensitive macroscopic Na⁺ conductance in this membrane, and thereby decreases the net driving force for K⁺ exit across the membrane, resulting in an inhibition of K⁺ secretion. SMX in the lumen or bath had no effect on the CCD.

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α-Helical transmembrane peptides: A “Divide and Conquer” approach to membrane proteins

Bordag¹,

Keller²

2010

Chemistry and Physics of Lipids

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Expression of an Artificial Cl? Channel in Microperfused Renal Proximal Tubules

Cited by 3 publications

References 17 publications

Claudin-2–deficient mice are defective in the leaky and cation-selective paracellular permeability properties of renal proximal tubules

Claudin-2–deficient mice are defective in the leaky and cation-selective paracellular permeability properties of renal proximal tubules

Effect of Trimethoprim-Sulfamethoxazole on Na<sup>+</sup> and K<sup>+</sup> Transport Properties in the Rabbit Cortical Collecting Duct Perfused in vitro

α-Helical transmembrane peptides: A “Divide and Conquer” approach to membrane proteins

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