Determination of delta psi, delta pH and the proton electrochemical gradient in isolated cholinergic synaptic vesicles |
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Authors: | I Angel D M Michaelson |
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Affiliation: | The George S. Wise Center for Life Sciences, Department of Biochemistry, Tel-Aviv University, Tel-Aviv, Israel |
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Abstract: | The electrical potential (Δψ) of intact cholinergic synaptic vesicles was measured in the presence and absence of the proton translocator carbonyl cyanide p-trifluoromethoxy-phenylhydrazone (FCCP), and the results were utilized to calculate the vesicular proton chemical gradient (ΔpH) and proton electrochemical potential . At external pH = 7.4 the vesicles maintain a proton electrochemical gradient of (positive inside) which is composed of (negative inside) and (acidic inside). The proton chemical gradient (ΔpH) increases as a function of pHout whereas the vesicular electrical potential (Δψ) is only slightly affected by the external pH. Consequently, is larger at basic external pH values ( at pHout = 9.0) and smaller at acidic external pH values ( at (pHout = 5.6). The possible physiological role of the electrochemical potentials in maintaining high concentrations of acetylcholine within the cholinergic synaptic vesicle is discussed. |
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