title: Iron centres and rate-limiting spans in the respiratory chains of mitochondria from adult and fetal rats.
abstract: The respiratory chain is a mosaic of complexes functionally linked through the mobile intermediates ubiquinone and cytochrome c. Changes in content of complexes that are not rat-limiting might not be reflected in the overall respiratory rate but may be revealed by titration with specific inhibitors. Oxidation of succinate by membranes of liver mitochondria from fetal, adult and starved rats was titrated with antimycin. Initial respiratory rates were similar but antimycin-titration curves were markedly different. The results indicate that the content of Complex III (cytochrome b-c1 span) is much lower in mitochondria from fetal and starved adult rats than in controls. In no case however is Complex III initially rat-limiting, and in fetal and starved adult rats it seems that a much lower content of functional Complex III is required to sustain a given respiratory rate. A possible explanation is a compensatory optimization of the pool function of ubiquinone, through increases in its content or its mobility in the mitochondrial membrane.
mesh_terms: D000375:Aging; D000818:Animals; D003580:Cytochromes / Q000378:metabolism*; D008099:Liver / Q000196:embryology; D008930:Mitochondria, Liver / Q000378:metabolism* / Q000648:ultrastructure; D010101:Oxygen Consumption; D051381:Rats; D013217:Starvation / Q000378:metabolism*; D014451:Ubiquinone / Q000378:metabolism
chemical_list: D003580:Cytochromes; D014451:Ubiquinone