Basolateral na+ pump modulates apical na+ and k+ conductances in
rabbit cortical collecting ducts_.
Muto, Shigeaki, Yasushi Asano, Donald Seldin, and Gerhard Giebisch.
1Department of Nephrology, Jichi Medical School, Minamikawachi,
Kawachi, Tochigi, 329-0498 Japan; Department of Internal Medicine,
2University of Texas Southwestern Medical Center at Dalas, Dalas, TX
75235; and 3Department of Cellular and Molecular Physiology, Yale
University School of Medicine, New Haven, CT 06520
APStracts 5:0172F, 1998.
Previous studies indicated that an acute elevation of peritubular K+
enhances K+ secretion and Na+ reabsorption in the isolated perfused
cortical collecting duct (CCD) from rabbit kidneys (21). To determine
the underlying cellular mechanisms, we used microelectrode techniques
to assess the membrane properties of collecting duct cells in
isolated perfused CCDs of control and desoxycorticosterone acetate
(DOCA)-treated rabbits following acute stimulation of the basolateral
Na+, K+ pump by rapidly increasing the bath solution from 2.5 to 8.5
mM K+. This induced in both groups of tubules, first, a short-lasting
hyperpolarization and second, a sustained phase of depolarization of
transepithelial, basolateral, and apical membrane voltages. Whereas
the transepithelial conductance (GT) and fractional apical membrane
resistance (fRA) remained unchanged during the initial phase of
hyperpolarization, during the depolarization GT increased and fRA
decreased. Perfusion of the lumen with solutions containing either
amiloride or Ba2+ attenuated the high K+-induced apical electrical
changes, and basolateral strophanthidin abolished both apical and
basolateral electrical responses during elevation of K+ in the bath.
From these results we conclude: 1) Acute elevation of basolateral K+
activates the basolateral Na+, K+ pump, which secondarily elevates
the apical Na+ and K+ conductances; 2) DOCA pretreatment increases
the basolateral K+ conductance and auguments the response to the rise
of K+ of both basolateral Na+, K+ pump activity and apical cation
conductances.
Received 8 July 1998; accepted in final form 24 July 1998.
APS Manuscript Number F162-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 20 October 1998