Basolateral Membrane Properties of Sodium-absorbing Epithelia

The relation between intracellular Na+ activities, (Na)c, determined employing Na+-selective microelectrodes, and the rates of active Na+ absorption, INa, by rabbit descending colon was examined when INa was varied over a wide range by chronic dietary Na+ deprivation. (Na)c averaged 13 mM and was independent of INa over a sixfold range. Further, the ratios of the slope resistance of the apical membrane (rm) to that of the basolateral membrane (rs) (i.e. rm/rs) in low-transporters (control diet) and high-transporters (Na+-deprived) did not differ significantly inspite of the fact that the Na+ conductance of the apical membranes of high-transporters was, on the average, three times greater than that of the low-transporters. These findings, together with the results reported by other laboratories, strongly suggest that the aldosterone-induced increase in the conductance of the apical membrane to Na+ and, in turn, the rate of entry of Na+ into the absorptive cells are followed by parallel increases in the ability of cells to extrude Na+ across the basolateral membrane in the absence of a sustained increase in (Na)c as well as the conductance of that barrier.

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Influence of barium on the effects of phenylalanine in proximal tubules

Rehwald¹,

Messner²,

Läng³

1986

Pflugers Arch.

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The present study was designed to further test for the role of peritubular potassium conductance in the repolarization of peritubular cell membrane during sustained stimulation of sodium coupled transport by phenylalanine. To this end the potential difference across the peritubular cell membrane (PDpt) has been recorded continuously, while 10 mmol/l phenylalanine (Phe) were added to the luminal perfusate, both in the presence or absence of peritubular or luminal barium (1 mmol/l). In the absence of phenylalanine and barium, PDpt amounts to -65.5 +/- 2.2 mV. Phe leads to a rapid depolarization of the peritubular cell membrane by +36.2 +/- 2.2 mV within 30 s, followed by an almost complete repolarization by -28.9 +/- 2.6 mV within 7 min. In the presence of barium in peritubular perfusate, the depolarization following Phe is +24.3 +/- 2.6 mV and the repolarization almost abolished (-4.3 +/- 0.9 mV). In the presence of barium in luminal perfusate, Phe leads to a depolarization by +35.7 +/- 2.4 mV followed by a repolarization of -17.0 +/- 3.2 mV within 7 min. It is concluded that the repolarization during sustained stimulation of sodium coupled transport is in large part due to alterations of peritubular potassium conductance.

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Basolateral Membrane Properties of Sodium-absorbing Epithelia

Cited by 4 publications

References 45 publications

Biology Of Sodium‐Absorbing Epithelial Cells: Dawning of a New Era

Biology Of Sodium‐Absorbing Epithelial Cells: Dawning of a New Era

Cell Na+ activities and transcellular Na+ absorption by descending colon from normal and Na+-deprived rabbits

Influence of barium on the effects of phenylalanine in proximal tubules

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