Tributyltin and mitochondria: new evidence in support of an uncoupling mechanism and a further characterisation of the transport mechanism

New evidence is given to support the hypothesis that the tributyltin compound (TBT) is an uncoupler of the oxidative phosphorylation in mitochondria. By means of an Arrhenius plot, it has been demonstrated that the transport kinetic of the TBT compound in mitochondria behaves in a manner which is similar to that obtained using classical uncouplers. The break point at 17 degreesC observed in the Arrhenius plot is interpreted as due to a phase change in the lipidic bilayer, since the TBT compound, like uncouplers and mobile carriers, is sensitive to the phospholipidic phase change. Therefore, we can confirm our previous hypothesis that, as TBT is an uncoupler it, like uncouplers, crosses the biological membranes by means of an electrophoretic mechanism. An understanding of this behaviour is essential when an explanation of the neurotoxicity of TBT is required. (C)