Energy-dependent accumulation of iron by isolated rat liver mitochondria. V. Effect of factors controlling respiration and oxidative phosphorylation.
1. Depending on the metabolic state, the addition of iron(III)-sucrose induces an inhibition or a stimulation of the respiration rate when added to isolated rat liver mitochondria. 2. Under conditions identical to those used in the accumulation studies (Romslo, I. and Flatmark T. (1973) Biochim. Biophys. Acta 305, 29-40), the ferric complex induces a decrease in the oxygen uptake concomitant to an oxidation of cytochromes c (+c1) and a(+a3). These results suggest that ferric iron is reduced to ferrous iron by the respiratory chain prior to or simultaneously with its energy-dependent accumulation. 3. On the other hand, the addition of iron(III)-sucrose induces a stimulation of respiration in State 4 and State 3 provided Mg-2+ is present in the suspending medium. In contrast to Ca-2+, iron stimulates State 4 respiration in a cyclic process only within narrow concentration limits; at concentrations of iron above 100 mu M the respiration remains in the activated state until anaerobiosis. The stimulation of State 4 respiration is more pronounced with succinate than with NAD-linked substrates, a difference which partly may be attributed to a stimulation of the succinate dehydrogenase complex. 4. The stimulation of respiration by iron is approx. 3 times higher in State 3 than in State 4 and this difference can be attributed to a stimulation of the adenine mucleotide exchange reaction in State 3 with a concomitant increase in the rate of oxidative phosphorylation, although the P/O ration is slightly diminished.
D000227:Adenine Nucleotides / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D003580:Cytochromes / Q000378:metabolism; D005420:Flavoproteins / Q000378:metabolism; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats; D013385:Succinate Dehydrogenase / Q000378:metabolism; D013386:Succinates / Q000378:metabolism
D000227:Adenine Nucleotides; D003580:Cytochromes; D005420:Flavoproteins; D013386:Succinates; D007501:Iron; D013385:Succinate Dehydrogenase; D008274:Magnesium