Approaches to characterize by density-fractionation age-dependent properties of reticulocyte mitochondria

Mitochondria from rabbit reticulocytes of varying maturity were prepared by means of two different methods and separated in sucrose and Percoll density gradients. A mechanical method of cell disintegration under isotonic conditions followed by centrifugation in a Percoll density gradient proved to be adequate to reflect the physiological conditions. "Young" mitochondria exhibit in this system greater density and higher specific activity of cytochrome oxidase.