In Elodea densa leaves, ethanol up to 0.17 M stimulates H+ extrusion activity. This effect is strictly dependent on the presence of K+ in the medium and is suppressed by the presence of the plasmalemma H+-ATPase inhibitor vanadate. Stimulation of H+ extrusion is associated with (a) a decrease in cellular ATP level, (b) a marked hyperpolarization of transmembrane electrical potential, and (c) an increase in net K+ influx. These results suggest that ethanol-induced H+ extrusion is mediated by an activation of the plasma membrane ATP-dependent, electrogenic proton pump. This stimulating effect is associated with an increase of cell sap pH and of the capacity to take up the weak acid 5,5-dimethyloxazolidine-2,4-dione, which is interpretable as due to an increase of cytosolic pH. This indicates that the stimulation of H+ extrusion by ethanol does not depend on a cytosolic acidification by products of ethanol metabolism. The similarity of the effects of ethanol and those of photosynthesis on proton pump activity in E. densa leaves suggests that a common metabolic situation is responsible for the activation of the ATP-dependent H+-extruding mechanism.
Ethanol-Induced Activation of ATP-Dependent Proton Extrusion in Elodea densa Leaves / M.T. Marrè, A. Venegoni, A. Moroni. - In: PLANT PHYSIOLOGY. - ISSN 0032-0889. - 100:3(1992 Nov), pp. 1120-1125. [10.1104/pp.100.3.1120]
Ethanol-Induced Activation of ATP-Dependent Proton Extrusion in Elodea densa Leaves
A. Moroni
1992
Abstract
In Elodea densa leaves, ethanol up to 0.17 M stimulates H+ extrusion activity. This effect is strictly dependent on the presence of K+ in the medium and is suppressed by the presence of the plasmalemma H+-ATPase inhibitor vanadate. Stimulation of H+ extrusion is associated with (a) a decrease in cellular ATP level, (b) a marked hyperpolarization of transmembrane electrical potential, and (c) an increase in net K+ influx. These results suggest that ethanol-induced H+ extrusion is mediated by an activation of the plasma membrane ATP-dependent, electrogenic proton pump. This stimulating effect is associated with an increase of cell sap pH and of the capacity to take up the weak acid 5,5-dimethyloxazolidine-2,4-dione, which is interpretable as due to an increase of cytosolic pH. This indicates that the stimulation of H+ extrusion by ethanol does not depend on a cytosolic acidification by products of ethanol metabolism. The similarity of the effects of ethanol and those of photosynthesis on proton pump activity in E. densa leaves suggests that a common metabolic situation is responsible for the activation of the ATP-dependent H+-extruding mechanism.File | Dimensione | Formato | |
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