Electrophysiology of sodium-coupled transport in proximal renal tubules

Läng, Florian; Messner, G.; Rehwald, Wolfgang G

doi:10.1152/ajprenal.1986.250.6.f953

Cited by 73 publications

(77 citation statements)

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“…Moreover, the decrease in uptake rate after sodium replacement should be greater than for a similar change in PD produced by other methods. Finally, high uptake fluxes should cause sodium-dependent depolarization of liver cells, as has been reported for other sodium-coupled solutes (28)(29)(30). Each of these predictions was confirmed.…”

Section: Introductionsupporting

confidence: 76%

Hepatic oleate uptake. Electrochemical driving forces in intact rat liver.

Weisiger

Fitz²,

Scharschmidt

1989

J. Clin. Invest.

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Recent observations suggest that the hepatic uptake of oleate may be sodium coupled. To assess the electrochemical forces driving fatty acid uptake, we used microelectrodes to monitor continuously the electrical potential difference across the plasma membrane in the perfused rat liver while simultaneously monitoring the rate of tracer VHioleate uptake from 1% albumin solutions. Isosmotic cation or anion substitution was used to vary the potential difference over the physiologic range. Depolarization of cells from -29 to -19 mV by substituting gluconate for chloride reduced steady-state oleate uptake by 34%. Conversely, hyperpolarization of cells to -52 mV by substituting nitrate for chloride increased uptake by 41%. Replacement of perfusate sodium with choline depolarized the cells to -18 mV and reduced uptake by 58%, an amount greater than expected from the degree of depolarization alone. Oleate in higher concentrations (1.5 mM in 2% albumin) depolarized cells by 3 mV in the presence of sodium, but had no effect in sodium-free buffer. These results suggest that a portion of oleate uptake in the intact liver occurs by electrogenic sodium cotransport. Uptake appears to be driven by both the electrical and sodium chemical gradients across the plasma membrane.

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Section: Introductionsupporting

confidence: 76%

Hepatic oleate uptake. Electrochemical driving forces in intact rat liver.

Weisiger

Fitz²,

Scharschmidt

1989

J. Clin. Invest.

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“…Epithelial transport, accomplished by the entry or extrusion of osmotically active substances at the two cellular membranes, represents a continuous challenge to cell volume constancy, since slight changes in the large apical or basolateral fluxes could lead to rapid changes in cell volume. For example, in intestine, gallbladder and renal proximal tubules the luminal uptake of substrates by Na + -coupled transport tends to swell the cells, leading to volume regulatory activation of K + channels in the basolateral cell membrane (Beck et al, 1991(Beck et al, , 1994Breton et al, 1996;Cemerikic and Sackin, 1993;Furlong and Spring, 1990;Harvey, 1994;Lang et al, 1986;Lau et al, 1984;Reuss and Cotton, 1994;Schultz, 1994;Turnheim, 1994). Moreover, epithelia, being interfaces between the internal and the external environment of the organism, can experience changes of extracellular osmolarity.…”

mentioning

confidence: 99%

Hypotonicity induced K+ and anion conductive pathways activation in eel intestinal epithelium

Lionetto

Giordano

Nuccio

et al. 2005

Journal of Experimental Biology

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“…The proximal convoluted tubule normally reabsorbs 90% of filtered glucose coupled with sodium and the remaining 10% is reabsorbed by more distal nephron segments (Lang, 1986). The fact that sodium excretion increased following steviol infusion, in spite of an unchanged glomerular filtration rate, may be explained by inhibition of the glucose reabsorption in the proximal tubules.…”

Section: Discussionmentioning

confidence: 99%

Steviol effect, a glycoside of Stevia rebaudiana, on glucose clearances in rats

2009

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Stevia rebaudiana, a South American plant normally used as a natural herbal sweetener, has been suggested as exerting beneficial effects on human health, including as an antihypertensive and antihyperglycemic. The present experiment was undertaken to evaluate the renal excretion of steviol, the aglycone of several natural products extracted from the leaves of S. rebaudiana, and to clarify the actual participation of this compound on the renal excretion of glucose in rats, which has been previously suggested as the preferential action of steviol on the Na + -glucose renal tubular transport system. Steviol was obtained by enzymatic hydrolysis of stevioside with pectinase. Thirty normal male Wistar rats weighing 345 g were used. After a control period, steviol was infused iv at three doses (0.5, 1.0 and 3.0 mg.kg -1 /h), according to classical clearance techniques. During all the experiments no significant changes in inulin clearance (C in ) and p-aminohipuric acid clearance (C PAH ) were observed. Administration of steviol resulted in a statistically significant increase in the fractional sodium excretion (FeNa + ), fractional potassium excretion (FeK + ), urinary flow as percent of glomerular filtration rate (V/GFR) and glucose clearance (C G ) when compared to controls, but these effects were absent with the dose of 0.5 mg.kg -1 /h. The steviol clearance (C S ) was higher than the C in and lower than the C PAH at all the doses employed in this study. The data suggest that steviol is secreted by renal tubular epithelium, causing diuresis, natriuresis, kaliuresis and a fall in renal tubular reabsorption of glucose.Keywords: renal function, Stevia rebaudiana, steviol, renal excretion of glucose. O efeito do esteviol, um glicosídeo da Stevia rebaudiana, no clearance da glicose em ratos ResumoStevia rebaudiana, uma planta da América do Sul usada como adoçante natural, parece exercer efeitos benéficos para a saúde humana, incluindo ação anti-hipertensiva e anti-hiperglicêmica. No presente trabalho objetivamos avaliar a excreção renal do esteviol, uma aglicona extraída das folhas de S. rebaudiana, e elucidar a participação deste composto na excreção renal de glicose em ratos, o qual foi sugerido agir no sistema de transporte tubular renal Na + -glicose. O esteviol foi obtido por hidrólise enzimática com pectinase. Foram usados 30 ratos Wistar machos e pesando 345 g. Após um período controle, o esteviol foi infundido iv em três doses (0,5, 1,0 e 3,0 mg.kg -1 /h) de acordo com técnicas clássicas de clearance. Durante os experimentos não houve alterações significantes no clearance da inulina (C in ) e do ácido-aminohipúrico (C PAH ). A administração de esteviol resultou em um aumento estatisticamente significante na excreção fracional de sódio (FeNa + ) e potássio (FeK + ), no fluxo urinário como porcentagem da taxa de filtração glomerular (V/GFR) e do clearance de glicose (C G ) quando comparados aos animais controles, embora estes efeitos estivessem ausentes na dose de 0,5 mg.kg -1 /h. O clearance de esteviol (C...

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Electrophysiology of sodium-coupled transport in proximal renal tubules

Cited by 73 publications

References 0 publications

Hepatic oleate uptake. Electrochemical driving forces in intact rat liver.

Hepatic oleate uptake. Electrochemical driving forces in intact rat liver.

Hypotonicity induced K+ and anion conductive pathways activation in eel intestinal epithelium

Steviol effect, a glycoside of Stevia rebaudiana, on glucose clearances in rats

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