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

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.

Key Words:

• membrane potentials
• lipid monolayers
• oxygen consumption
• mitochondria
• hepatocytes