Changes in Interfacial Potentials Induced by Carbonylcyanide Phenylhydrazone Uncouplers: Possible Role in Inhibition of Mitochondrial Oxygen Consumption and Other Transport Processes

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Abstract
The charged and uncharged forms of carbonyl-cyanide phenylhydrazone uncouplers bind to phosphatidylcholine monolayers in a dose-dependent fashion, inducing changes in the interfacial potential of these model membranes. The interfacial potential change produced by the charged un-coupler is composed of a double-layer potential and an internal electrostatic potential (boundary and/or dipole). Changes in double-layer potential induced by the uncouplers in mitochondrial membranes can explain both the inhibition of oxygen consumption (QO2) caused by the uncouplers and the competition shown by succinate when mitochondria are respiring in the presence of rotenone. From these results and from dose-response curves of QO2 versus uncoupler concentrations, we conclude that 1 μM is an upper limit for free uncoupler concentration in the medium to avoid unwanted side effects during cell physiology studies that require total mitochondrial uncoupling.