Size and shape of isolated rat liver mitochondria.

Abstract

The dimensions of unfixed rat liver mitochondria, isolated in 0.44 M sucrose, were measured on photomicrographs taken by phase-contrast microscopy. The lengths ranged from the limit of resolution of the microscope (ca. 0.2 μ) to ca. 5 μ. The smallest measured particle had a calculated volume of 0.008 μ3 and the largest 3.85 μ3. Separate fractions of mitochondria, in order of decreasing sedimentation rate and fragility (Can. J. Biochem. 44, 497), were found to range in mean size from 0.92 μ long × 0.59 μ in diameter (fraction I), through 0.84 μ × 0.59 μ (fraction III) to 0.60 μ × 0.48 μ (fraction V). The limitations and errors in the measurements have been discussed. While these measurements cannot be considered "correct" in an absolute sense, they more closely represent the actual size of unfixed isolated mitochondria than do previously reported measurements, and reliably allow size characterization of different fractions.