Potassium and Sodium Transport across Single Distal Tubules of <i>Amphiuma </i>

Wiederholt, Michael; Sullivan, W. James; Giebisch, Gerhard

doi:10.1085/jgp.57.5.495

Cited by 76 publications

(28 citation statements)

References 37 publications

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“…No direct effect of insulin on the net uptake of potassium by renal tubule cells would be required to produce this effect, since the reduction in plasma potassium concentration can be attributed to enhanced potassium uptake by the liver and skeletal muscle. If, on the other hand, insulin actually increases potassium transport into tubular cells, our data would be compatible with either an inhibitory effect of insulin on potassium secretion or an increase of intracellular potassium in a compartment that has no effect on potassium secretion (67).…”

Section: Discussionsupporting

confidence: 62%

The effect of insulin on renal handling of sodium, potassium, calcium, and phosphate in man.

DeFronzo¹,

Cooke²,

Andres³

et al. 1975

J. Clin. Invest.

1,035

418

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A B S T R A C T The effects of insulin on the renal handling of sodium, potassium, calcium, and phosphate were studied in man while maintaining the blood glucose concentration at the fasting level by negative feedback servocontrol of a variable glucose infusion. In studies on six water-loaded normal subjects in a steady state of water diuresis, insulin was administered i.v. to raise the plasma insulin concentration to between 98 and 193 PU/ml and infused at a constant rate of 2 mU/kg body weight per min over a total period of 120 min. The blood glucose concentration was not significantly altered, and there was no change in the filtered load of glucose; glomerular filtration rate (CIN) and renal plasma flow (CPAH) were unchanged. Urinary sodium excretion (UNaV) decreased from 401±46 (SEM) to 213+18 iteq/min during insulin administration, the change becoming significant (P < 0.02) within the 30-60-min collection period. Free water clearance (CH2o) increased from 10.6±0.6 to 13±0.5 ml/min (P <0.025); osmolar clearance decreased and urine flow was unchanged. There was no change in plasma aldosterone concentration, which was low throughout the studies, and a slight reduction was observed in plasma glucagon concentration. Urinary potassium (UKV) and phosphate (Ui.V) excretion were also both decreased during insulin administration; UKV decreased from 66±9 to 21±1 Meq/min (P < 0.005), and UrV decreased from 504±93 to 230 ±43 Ag/min (P <0.01). The change in UKV was associated with a significant reduction in plasma potassium concentration. There was also a statistically significant but small reduction in plasma phosphate concentration which was not considered sufficient alone to account for the large reduction in UPV. Urinary calcium excretion (UCaV) increased from 126±24 to 200±17 ug/min (P < 0.01).These studies demonstrate a reduction in UNaV associated with insulin administration that occurs in the absence of changes in the filtered load of glucose, glomerular filtration rate, renal blood flow, and plasma aldosterone concentration. The effect of insulin on CH2o suggests that insulin's effect on sodium excretion is due to enhancement of sodium reabsorption in the diluting segment of the distal nephron.

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Section: Discussionsupporting

confidence: 62%

The effect of insulin on renal handling of sodium, potassium, calcium, and phosphate in man.

DeFronzo¹,

Cooke²,

Andres³

et al. 1975

J. Clin. Invest.

1,035

418

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“…VTE was somewhat lower in vivo, on average -6 mV (Hoshi, Suzuki & Itoi, 1981; Cohen, Giebisch, Hansen, Teuscher & Wiederholt, 1984) to -15 mV (Teulon & Anagnostopoulos, 1982a), though on occasion VTE reached -35 mV in late portions of this segment (Teulon & Anagnostopoulos, 1982a). Initial determinations of intraluminal ion concentrations along the distal tubule of NecturUs in vivo revealed a substantial axial decline of luminal Na' and Cl-concentrations, consistent with the observed net NaCl absorption along this segment (Bott, 1962); subsequent work confirmed the decrease of Na+ concentration (Wiederholt, Sullivan & Giebisch, 1971; Garland, Henderson & Brown, 1975;Persson & Persson, 1983) and of total electrolyte concentration (Hoshi et al 1981) along the amphibian distal tubule. Tubule to plasma K+ concentration ratio showed variability, but it was essentially lower than 1-00 in the second half of the distal tubule of Necturus (Bott, 1962); this ratio was found to decline from -1P50 to 0-80 along the distal tubule of Amphiuma, (Wiederholt et al 1971) or display a large scatter and remain close to 1 00 in the second half of this segment in Necturus (Garland et al 1975).…”

Section: Introductionmentioning

confidence: 68%

“…Na+ and Cl-are physiologically absorbed in the amphibian and in the mammalian distal nephron, whereas K+ may be transported in either direction in both Amphiuma distal tubule (Wiederholt et al 1971) and mammalian distal convoluted tubule, depending on metabolic and nutritional conditions. The present data probably pertain to the control state defined by Wiederholt et al (1971), in which net K+ absorption prevails.…”

Section: Potas8iummentioning

confidence: 99%

“…Since water is absorbed in the amphibian distal tubule (Bott, 1962;Wiederholt et al 1971;Garland et al 1975), the decrease of luminal Na+ and Cl-concentrations longitudinally indicates that they are reabsorbed in this segment, including its late portion. K+ is normally absorbed in the l.d.t., but secretion is also possible under certain conditions (Wiederholt et al 1971).…”

Section: Introductionmentioning

confidence: 99%

“…K+ is normally absorbed in the l.d.t., but secretion is also possible under certain conditions (Wiederholt et al 1971). However, such studies do not provide information about the site (membrane) of the active step generating net ion transport.…”

Section: Introductionmentioning

confidence: 99%

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Cell and luminal activities of chloride, potassium, sodium and protons in the late distal tubule of Necturus kidney.

Anagnostopoulos

Planelles

1987

The Journal of Physiology

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SUMMARY1. Double-barrelled (selective vs. conventional) microelectrodes were used to assess the steady-state activities (a) of the ions Cl-, K+, Na+ and H' in peritubular blood capillaries (abld) and in cell (ace11) and lumen (alum) of the late distal tubule2. acl1, acm and abl were 5-5 + 0-3, 11P8 + 1I0 and 70 5 + 0-1 mm, respectively. They were used to compute the chemical potentials for Cl-across the three diffusive barriers of the tissue. Basolateral and apical membrane potentials were -74-3 + 1 1 and -60-1+2-0 mV, respectively (cell negative); the lumen was thus negative with respect to blood, by 13-6 + 1-5 mV. The electrochemical potential difference (e.p.d.) for Cl-of 42 mV across the apical membrane opposes Cl-absorption, implying active apical Cl-uptake, since Cl-is known to be absorbed in the l.d.t. Basolateral Cl-exit is favoured by an e.p.d. of 10 mV.3. aKe1 a Km and abl were 65-8 + 0-8, 2-5 + 0-1 and 2-5 + 0-1 mm, respectively. The electrochemical distribution of K+ indicates that K+ absorption, if present, proceeds against an adverse apical e.p.d. of 18 mV. Basolateral K+ distribution is close to its electrochemical equilibrium, suggesting high K+ permeability at this membrane.4. aea was 9 0 +0-4 mm, abd 71-0+0-3 mm, and a Na was approximated at about 9 mm. Diffusive Na+ entry from lumen to cell is favoured by an e.p.d. close to 65 mV. Basolateral Na+ exit must be active, since it proceeds against an e.p.d. of 130 mV.5. Cell, luminal and blood pH were 7-14 + 0 03, 6-52 + 0-08 and 7-37 + 0 04, respectively. The luminal electrochemical potential of H+ is higher than that of cell (by 91 mV) and blood (by 34 mV) indicating that proton secretion into the lumen must be active.6. The e.p.d. of each ion across the epithelium opposes, by its orientation, the established direction of net transepithelial ion transport, suggesting that the shunt pathway may serve only for back-diffusion.* The authors' names are in alphabetical order.

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