Electrophysiological evidence for the presence of an apical H(+)-ATPase in Malpighian tubules of Formica polyctena: intracellular and luminal pH measurements

Pflugers Arch. 1994 Feb;426(3-4):288-95. doi: 10.1007/BF00374784.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antiporters / metabolism
  • Ants / enzymology*
  • Cell Membrane / metabolism
  • Cytoplasm / metabolism
  • Electrochemistry
  • Electrophysiology
  • Hydrogen-Ion Concentration
  • Malpighian Tubules / enzymology*
  • Membrane Potentials / physiology
  • Microelectrodes
  • Potassium / metabolism
  • Potassium-Hydrogen Antiporters
  • Proton-Translocating ATPases / metabolism*
  • Proton-Translocating ATPases / physiology


  • Antiporters
  • Potassium-Hydrogen Antiporters
  • Proton-Translocating ATPases
  • Potassium