ROLE OF EDTA AND METALS IN MITOCHONDRIAL CONTRACTION

Studies comparing the state of hydration and dehydration of rat liver mitochondria to their content of ATP, Ca, and fatty acid, along with the rate of ATP hydrolysis, as well as microscopic appearance of mitochondria, have led to the following generalizations: 1. The competition between cationic translocations and water translocation for the available chemical energy (ATP) determines under many circumstances the water content of mitochondria. 2. Swelling of mitochondria by electron transport substrates is an example of the activation of the cationic translocations at the expense of water translocation. 3. Electron micrographic studies are interpreted to indicate that EDTA alone can cause condensation and dehydration of the mitochondrial matrix. However, both EDTA and substrate are necessary to remove appreciable quantities of water from mitochondrial intramembranous spaces. 4. Since the data in the accompanying report indicated that EDTA, in the absence of energy, decreased the permeability of mitochondrial membranes, it appears likely that ballooning of intramembranous spaces, following addition of EDTA, represents trapping of water between two semipermeable membranes following dehydration of mitochondrial matrix.