OSMOTIC AND METABOLIC ALTERATIONS OF MITOCHONDRIAL SIZE

Sustained contraction (dehydration) of rat liver mitochondria can be readily produced by increasing the tonicity of the outside media, provided Ca⁺⁺ is removed by EDTA, fatty acids are removed by albumin, and a source of chemical energy (mitochondrial substrate or ATP) is present. This was demonstrated both gravimetrically and turbidimetrically. It was also demonstrated that the net movement of sucrose and H₂O under altered conditions of tonicity in mitochondria was dependent on the state of the mitochondria; e.g., in the presence of EDTA, diffusion was blocked, both into and out of mitochondria, whereas, in the presence of EDTA and electron-transport substrates, movement of sucrose and water out of mitochondria was increased. In the presence of Ca⁺⁺, gramicidin, or fatty acids, diffusion of sucrose into and out of mitochondria is very rapid. Mitochondria obey osmotic law only after Ca⁺⁺ and fatty acids are removed from them.