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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/3467

Title: Cross-talk between ATP-regulated K+ channels and Na+ transport via cellular metabolism in frog skin principal cells
Authors: Urbach, V
VAN KERKHOVE, Emmy
Maguire, D
Harvey, BJ
Issue Date: 1996
Publisher: CAMBRIDGE UNIV PRESS
Citation: JOURNAL OF PHYSIOLOGY-LONDON, 491(1). p. 99-109
Abstract: Isolated frog skin epithelium, mounted in an Ussing chamber and bathed in standard NaCl Ringer solution, recycles K+ across the basolateral membrane of principal cells through an inward-rectifier K+ channel (Kir) operating in parallel with a Na+-K+-ATPase pump. Here we report on the metabolic control of the Kir channel using patch clamping, short-circuit current measurement and enzymatic determination of cellular (ATP (ATPi). 2. The constitutively active Kir channel in the basolateral membrane has the characteristics of an ATP-regulated K+ channel and is now classed as a KATP channel. In excised inside-out patches the open probability (Po) of KATP channels was reduced by ATPi with half-maximum inhibition at an ATPi concentration of 50 microM. 3. ATPi measured (under normal Na+ transport conditions) with luciferin-luciferase was 1.50 +/- 0.23 mM (mean +/- S.E.M.; range, 0.4-3.3 mM n = 11). Thus the KATP channel would be expected to be inactive in intact cells if ATPi was the sole regulator of channel activity. KATP channels which were inactivated by 1 mM ATPi in excised patches could be reactivated by addition of 100 microM ADP on the cytosolic side. When added alone, ADP blocks this channel with half-maximal inhibition at [ADPi] > 5 mM. 4. Sulphonylureas inhibit single KATP channels in cell-attached patches as well as the total basolateral K+ current measured in frog skin epithelia perforated with nystatin on the apical side. 5. Na+-K+-ATPase activity is a major determinant of cytosolic ATP. Blocking the pump activity with ouabain produced a time-dependent increase in ATPi and reduced the open probability of KATP channels in cell-attached membranes. 6. We conclude that the ratio of ATP/ADP is an important metabolic coupling factor between the rate of Na+-K+ pumping and K+ recycling.
Notes: LIMBURGS UNIV CENTRUM,DEPT PHYSIOL,B-3590 DIEPENBEEK,BELGIUM.Urbach, V, NATL UNIV IRELAND UNIV COLL CORK,DEPT PHYSIOL,WELLCOME TRUST CELLULAR PHYSIOL RES UNIT,CORK,IRELAND.
URI: http://hdl.handle.net/1942/3467
Link to publication: http://jp.physoc.org/cgi/content/abstract/491/Pt_1/99
ISI #: A1996TX80400009
ISSN: 0022-3751
Type: Journal Contribution
Appears in Collections: Research publications

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