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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/3610

Title: Electrophysiological evidence for the presence of an apical h+-atpase in malpighian tubules of formica-polyctena - intracellular and luminal ph measurements
Authors: ZHANG, SL
LEYSSENS, Anne
VAN KERKHOVE, Emmy
WELTENS, R
VAN DRIESSCHE, Willy
STEELS, Paul
Issue Date: 1994
Publisher: SPRINGER VERLAG
Citation: PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY, 426(3-4). p. 288-295
Abstract: Cellular and luminal pH of isolated ant Malpighian tubules were measured in different bath K+ concentrations using double-barrelled pH microelectrodes. The electrochemical gradient for H+ across the basolateral and the apical cell membranes was estimated. In control Ringer (51 mmol/l K+) cell and luminal pH were alkaline with respect to the basolateral solution: 7.77 and 7.36, respectively, versus 7.25. On lowering basolateral K+ concentration to 5 mmol/l or increasing it to 113 mmol/l, luminal pH and to a lesser extent cell pH followed: luminal pH changed to 7.14 and 7.43 and cell pH to 7.69 and 7.82. respectively. In all conditions a cell inward electrochemical gradient for protons across both membranes was observed. Increasing basolateral K+ concentration, which was positively correlated with secretion rate, decreased the cell inwardly directed apical proton gradient; moreover, the apical membrane potential difference decreased as well, from -93 mV in 5 mmol/l K+ to -65 mV in 113 mmol/l K+. Therefore the turnover rate of the electrogenic active proton pump at the apical membrane is facilitated in a high basolateral K+ concentration. The calculated electromotive force of this pump is -159 mV. Comparing the proton with the K+ electrochemical gradient, taken from another study in the same experimental conditions, we find that the apical proton electrochemical gradient can drive K+ extrusion into the lumen for each value of secretion rate.
Notes: LIMBURGS UNIV CTR,DEPT MED BASISWETENSCHAPPEN,FYSIOL LAB,B-3590 DIEPENBEEK,BELGIUM. KATHOLIEKE UNIV LEUVEN,FYSIOL LAB,B-3000 LOUVAIN,BELGIUM.
URI: http://hdl.handle.net/1942/3610
DOI: 10.1007/BF00374784
ISI #: A1994MX01400016
ISSN: 0031-6768
Type: Journal Contribution
Appears in Collections: Research publications

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