Abstract
Regulation of the energy metabolism in mammals ultimately depends on regulatory processes at the cellular level, which include a regulation of the oxidative phosphorylation in mitochondria. A review of the literature on the regulation of cellular and mitochondrial oxygen uptake as related to the level of extracellular Pi leads to the suggestion that the concentration of plasma Pi may well be essential for the regulation of energy metabolism in the animal kingdom and in humans in different clinical situations. The role of Pi in the regulation of the rate of O2 consumption is discussed.