title: Regulation of mitochondrial respiration by inorganic phosphate; comparing permeabilized muscle fibers and isolated mitochondria prepared from type-1 and type-2 rat skeletal muscle.
abstract: ADP is generally accepted as a key regulator of oxygen consumption both in isolated mitochondria and in permeabilized fibers from skeletal muscle. The present study explored inorganic phosphate in a similar regulatory role. Saponin permeabilized fibers and isolated mitochondria from type-I and type-II muscle from male Wistar rats were prepared. Respiration was measured while the medium P(i) concentration was gradually increased. The apparent K(m) values for P(i) were 607 +/- 17 microM and 405 +/- 15 microM (P < 0.0001) for type-I and type-II fibers, respectively. For isolated mitochondria the values were significantly lower than type-1 permeabilized fibers, 338 +/- 130 microM and 235 +/- 30 microM (P < 0.05), but not different with respect to fiber type. The reason for this difference in K(m) values in the permeabilized muscle is unknown, but a similar pattern has been observed for K(m) of ADP. Our data indicate that phosphate may play a role in regulation of oxygen consumption in vitro and in vivo.
authors.affiliation: Department of Biomedical Sciences, NMR Center, Faculty of Health Sciences,The Panum Institute, The University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen, Denmark. morten@forsoegsperson.dk
authors.forename: Morten
authors.initials: M
authors.lastname: Scheibye-Knudsen
authors.forename: Bjørn
authors.initials: B
authors.lastname: Quistorff
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000818:Animals; D019069:Cell Respiration / Q000502:physiology*; D002474:Cell-Free System / Q000378:metabolism; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism*; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010101:Oxygen Consumption / Q000502:physiology; D010710:Phosphates / Q000032:analysis / Q000378:metabolism*; D051381:Rats
chemical_list: D010710:Phosphates; D000244:Adenosine Diphosphate