Regulation of mitochondrial respiration by inorganic phosphate; comparing permeabilized muscle fibers and isolated mitochondria prepared from type-1 and type-2 rat skeletal muscle

Eur J Appl Physiol. 2009 Jan;105(2):279-87. doi: 10.1007/s00421-008-0901-9. Epub 2008 Nov 7.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Diphosphate / metabolism
  • Animals
  • Cell Respiration / physiology*
  • Cell-Free System / metabolism
  • Male
  • Mitochondria, Muscle / metabolism*
  • Muscle Fibers, Fast-Twitch / metabolism*
  • Muscle Fibers, Slow-Twitch / metabolism*
  • Oxidative Phosphorylation
  • Oxygen Consumption / physiology
  • Phosphates / analysis
  • Phosphates / metabolism*
  • Rats


  • Phosphates
  • Adenosine Diphosphate