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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 | Source: | 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. | Keywords: | ION-SENSITIVE MICROELECTRODES; BASOLATERAL POTASSIUM CONCENTRATION; SECRETION RATE | Document URI: | http://hdl.handle.net/1942/3610 | DOI: | 10.1007/BF00374784 | ISI #: | A1994MX01400016 | Type: | Journal Contribution |
Appears in Collections: | Research publications |
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