Influence of mitochondrial inhibitors on the respiration and energy-dependent uptake of iodide by thyroid slices

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Abstract
The influence of mitochondrial inhibitors, including oligomycin, antimycin and rote none, on the iodide and O2 uptake and the nucleotide content of incubated sheep thyroid slices was investigated. Each inhibitor strongly suppressed both iodide and O2 uptake, and decreased the nucleoside triphosphate content of the slices. In most cases the addition of glucose or mitochondrial substrates restored iodide uptake in inhibitor-treated slices. Inhibitor concentrations sufficient to inhibit iodide uptake strongly had only slight effects on the thyroidal Na+ + K+-activated ATPase. The inhibitors produce their effects by the inhibition in vivo of mitochondrial oxi-dative phosphorylation. ATP synthesis appears essential for iodide uptake to occur, and the high-energy intermediates (or energized state) of oxidative phosphorylation cannot be used to energize the uptake process. To a limited extent glycolytic ATP synthesis can support iodide uptake, which is therefore not exclusively dependent on aerobic metabolism. The mechanism of energy-linked iodide uptake is discussed.