NATURE OF RESPIRATORY STIMULATION IN HYPERTHYROIDISM - THE REDOX BEHAVIOR OF CYTOCHROME-C

Hyperthyroid mitochondria show an increased K-m and V-max in the high affinity phase of cytochrome oxidase kinetics, During inhibitor titrat ions, cytochrome c shows a different redox behaviour in hyperthyroid w ith respect to protonophore-treated euthyroid mitochondria. The observ ations are discussed in terms of a different regulation of electron in put and output into the respiratory chain during slip and leak types o f uncoupling. In hyperthyroid mitochondria during inhibitor titrations , the pattern of the relationship between uncoupler-induced extra-resp iration and membrane potential is highly non-linear. The complex natur e of the respiratory stimulation in hyperthyroid mitochondria is discu ssed.