Oxidative phosphorylation. Halide-dependent and halide-independent effects of triorganotin and trioganolead compounds on mitochondrial functions.

Abstract

1. Each of five triorganotin and five triorganolead compounds was shown to perturb mithochondrial functions in three different ways. One is dependent and two are independent of Cl- in the medium. 2. Structure-activity relationships for the three interactions are described, and compounds suitable as tools for the separate study of each process are defined. 3. In a Cl- -containing medium trimethyltin, triethyltin, trimethyl-lead, triethyl-lead and tri-n-propyl-lead all produce the same maximum rate of ATP hydrolysis and O2 uptake; this rate is much less than that produced by uncoupling agents such as 2,4-dinitrophenol. 4. Increase in ATP hydrolysis and O2 uptake are measures on energy ultilization when triogranotin and triorganolead compounds bring about an exchange of external C1- for intramitochondrial OH- ions. Possible rate-limiting steps in this process are discussed. 5. In a C1- -containing medium ATP synthesis linked to the oxidation of beta-hydroxybutyrate or reduced cytochrone c is less inhibited by triethyltin or triethyl-lead than is ATP synthesis linked to the oxidation of succinate, pyruvate or L-glutamate. 6. The inhibition of ATP synthesis linked to the oxidation of both beta-hydroxybutyrate and reduced cytochrome c consists of two processes: one is a limited uncoupling and is C1- -dependent and the other is a C1- -independent inhibition of the energy-conservation system. 7. The different sensitivities to inhibition by triethyltin of mitochondrial functions involving the oxidation of beta-hydroxybutyrate and succinate are compared and discussed.