Intracellular potassium in cells of the proximal tubule of necturus maculosus

Khuri, Raja N.; Hajjar, Jean-Jacques; Agulian, S. K.; Bogharian, K.; Kalloghlian, A.; Bizri, Hana

doi:10.1007/bf00586856

Cited by 34 publications

(17 citation statements)

References 8 publications

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“…Measurements of the intracellular ion content of control kidneys during summer and winter are included. The control values for intracellular composition in Table IV are in good agreement with the previous observations of Whittembury et al, 1961 (Na + = 37, K + = 108, CI-= 32 mM/ liter); Giebisch, 1961 (Na + = 40, K + = 90 mM/liter); and Khuri et al, 1972 (Na + = 38, K + = 103 mM/liter).…”

Section: Dependence Of Cell Composition On Extraceuular Na + or Naclsupporting

confidence: 89%

“…Also, peritubular membrane potential should remain relatively constant. Since most of the kidney wet weight is made up of proximal tubules, the tissue results primarily reflect the composition of proximal tubule cells (Whittembury et al, 1961;Giebisch, 1961;Khuri et al, 1972). Table I lists the effects of replacement of 45% of the extracellular Na ÷ by choline, K +, Li +, or of tetramethyl ammonium (TMA) on tissue H.~O, cell composition, and peritubular membrane PD.…”

Section: Tissue Analysismentioning

confidence: 99%

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Kinetics of Na+ transport in Necturus proximal tubule.

Spring¹,

Giebisch²

1977

The Journal of General Physiology

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A B S T R A C T The dependence of proximal tubular sodium and fluid reabsorption on the Na + concentration of the luminal and peritubular fluid was studied in the perfused Necturus kidney. Fluid droplets, separated by oil from the tubular contents and identical in composition to the vascular perfusate, were introduced into proximal tubules, reaspirated, and analyzed for Na ÷ and [~4C]mannitol. In addition, fluid transport was measured in short-circuited fluid samples by observing the rate of change in length of the split droplets in the tubular lumen. Both reabsorptive fluid and calculated Na fluxes were simple, saturable functions of the perfusate Na + concentration (Kin = 35-39 mM/liter, Vmax = 1.37 control value). Intracellular Na +, determined by tissue analysis, and open-circuit transepithelial electrical potential differences were also saturable functions of extracellular Na +. In contrast, net reabsorptive fluid and Na + fluxes were linearly dependent on intracellular Na + and showed no saturation, even at sharply elevated cellular sodium concentrations. These concentrations were achieved by addition of amphotericin B to the luminal perfusate, a maneuver which increased the rate of Na + entry into the tubule cells and caused a proportionate rise in net Na + flux. It is concluded that active peritubular sodium transport in proximal tubule cells of Necturus is normally unsaturated and remains so even after amphotericin-induced enhancement of luminal Na ÷ entry. Transepithelial movement of NaCI may be described by a model with a saturable luminal entry step of Na ÷ or NaCI into the cell and a second, unsaturated active transport step of Na + across the peritubular cell boundary.

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Section: Dependence Of Cell Composition On Extraceuular Na + or Naclsupporting

confidence: 89%

Section: Tissue Analysismentioning

confidence: 99%

Kinetics of Na+ transport in Necturus proximal tubule.

Spring¹,

Giebisch²

1977

The Journal of General Physiology

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“…Several authors report Na c between 38 and 45 mM and K c between 90 and 108 mu (Giebisch, 1961;Whittembury, Sugino & Solomon, 1961;Khuri etal., 1972). However, measurements with K-selective electrodes in Necturus proximal tubule cells give K activities of 58.7 raM, considerably lower than chemically determined values (Khuri et al, 1972). This K activity value for proximal tubule cells is surprisingly close to our calculated K activity for gallbladder cells (Table 4).…”

Section: Rt Pkmentioning

confidence: 51%

The electrical potential profile of gallbladder epithelium

Slegers

1975

J. Membrain Biol.

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Summary. In this study the relative ionic permeabilities of the cell membranes of Necturus gallbladder epithelium have been determined by means of simultaneous measurement of transmural and transmucosal membrane potential differences (PD) and by ionic substitution experiments with sodium, potassium and chloride ions. It is shown that the mucosal membrane is permeable to sodium and to potassium ions. The baso-lateral membrane PD is only sensitive to potassium ions. In both membranes chloride conductance is negligible or absent. The ratio of the resistances of the mucosal and baso-lateral membranes, RM/Rs, increases upon reducing the sodium concentration in the mucosal solution. The same ratio decreases when sodium is replaced by potassium which implies a greater potassium than sodium conductance in the mucosal membrane. The relative permeability of the shunt for potassium, sodium and chloride ions is: PK/PNa/Pcl = 1.81: 1.00:0.32.From the results obtained in this study a value for the PK/PNa ratio of the mucosal membrane could be evaluated. This ratio is 2.7. From the same data the magnitude of the electromotive forces generated across the cell membranes could be calculated. The EMF's are -15 mV across the mucosal membrane and -81 mV across the baso-lateral one. Due to the presence of the low resistance shunt the transmucosal membrane PD is -53.2 mV (cell inside negative) and the transmural PD is + 2.6 mV (serosal side positive). The change in potential profile brought about by the low resistance shunt favors passive entry of Na ions into the cell across the mucosal membrane. Calculations show that this passive Na influx is maximally 64 ~o of the net Na flux estimated from fluid transport measurements. The Cl-conductance of the baso-latera| membrane is too small to allow electrogenic coupling of C1 with Na transport across this membrane. Experiments with rabbit gallbladder epithelium indicate that the membrane properties in this tissue are qualitatively similar to those of Necturus gallbladder epithelium.Epithelial tissues involved in transmural Na transport have been divided into "tight" and "leaky" epithelia (Fr6mter & Diamond, 1972).Tight epithelia, such as amphibian skin and urinary bladder, are characterized by high transmural resistances and potential differences (PD).From ionic substitution experiments it was concluded that the transmural *Current address:

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“…Similar electrochemical gradients have been reported for certain other epithelial tissues such as frog skin (Jan~t~ek, Morel & Bourguet, 1968) and frog intestine (Lee & Armstrong, 1972). On the other hand, Khuri et al (1972) found K § to be near electrochemical equilibrium in the proximal tubular cells of Necturus kidney.…”

Section: Resultsmentioning

confidence: 93%

Distribution of Na+, K+ and Cl− between nucleus and cytoplasm inChironomus salivary gland cells

Palmer

Civan

1977

J. Membrain Biol.

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Summary. Previous studies of the electrochemical activity coefficients of intracellular Na + and K + have suggested that the free form of these ions may be unevenly distributed within the intracellular fluids. One possible site of such subcellular compartmentalization is the cell nucleus. In order to examine this possibility, the cells of Chironomus salivary glands were studied with conventional liquid ion-exchange microelectrodes sensitive to K + and CI-, with a new liquid ion-exchange microelectrode sensitive to Na + , and with open-tipped micropipets. Both the electrochemical activities for Na +, K + and CI-, and the electrical potential were the same on both sides of the nuclear membrane. The possibility was considered that a difference in the junction potentials within the nucleoplasm and cytoplasm might have masked a real difference in electrical potential between these two phases. To study that possibility, changes were induced in the junction potentials by altering the composition of the fluid filling the exploring micropipets. The results have suggested that the magnitudes of the junction potentials are the same on both sides of the nuclear envelope. The simplest interpretation of the data is that the chemical activities of Na +, K + and C1-are the same within the nucleus and cytoplasm. This suggests that other subcellular structures, possibly the endoplasmic reticulum and mitochondria, are responsible for subcellular compartmentalization.

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Intracellular potassium in cells of the proximal tubule of necturus maculosus

Cited by 34 publications

References 8 publications

Kinetics of Na+ transport in Necturus proximal tubule.

Kinetics of Na+ transport in Necturus proximal tubule.

The electrical potential profile of gallbladder epithelium

Distribution of Na+, K+ and Cl− between nucleus and cytoplasm inChironomus salivary gland cells

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