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Am J Physiol Renal Physiol 263: F453-F458, 1992;
0363-6127/92 $5.00
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AJP - Renal Physiology, Vol 263, Issue 3 453-F458, Copyright © 1992 by American Physiological Society

ARTICLES

Potassium conductance regulation by pH during volume regulation in rabbit proximal convoluted tubules

J. S. Beck, S. Breton, G. Giebisch and R. Laprade
Membrane Transport Research Group, University of Montreal, Canada.

When rabbit proximal convoluted tubules were microperfused in the presence of bicarbonate, a 90 mosmol hypotonic shock hyperpolarized the basolateral membrane by 5.5 +/- 1.4 mV, increased basolateral potassium selectivity (tK) from 0.30 +/- 0.02 to 0.45 +/- 0.02, and reduced the basolateral membrane resistance from 4,887 +/- 821 to 2,836 +/- 602 omega.cm. These data show that the hypotonic shock increased absolute basolateral potassium conductance. The same hypotonic shock elevated intracellular pH from 7.18 +/- 0.04 to 7.31 +/- 0.04. When bath pH was increased by 0.2 pH units (by reduction of CO2), intracellular pH rose by 0.13 +/- 0.01. In separate experiments this maneuver hyperpolarized the basolateral membrane by 5.0 +/- 0.8 mV and augmented basolateral tK from 0.58 +/- 0.06 to 0.68 +/- 0.04, suggesting that the basolateral potassium conductance is sensitive to pH changes of a magnitude similar to that evoked by a hypotonic shock. In the nominal absence of bicarbonate or presence of 0.5 mM 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) in the bath, the hypotonic shock caused a transient intracellular acidification, suggesting involvement of basolateral bicarbonate transport in the hypotonic shock-induced alkalinization. In the absence of bicarbonate, the hypotonic shock did not increase basolateral tK or induce hyperpolarization of the basolateral membrane. We conclude that the increase in potassium conductance observed during hypotonic shock is at least partly mediated by a bicarbonate-dependent, SITS-sensitive intracellular alkalinization.


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C. Bagnis, M. Marsolais, D. Biemesderfer, R. Laprade, and S. Breton
Na+/H+-exchange activity and immunolocalization of NHE3 in rat epididymis
Am J Physiol Renal Physiol, March 1, 2001; 280(3): F426 - F436.
[Abstract] [Full Text] [PDF]


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