Korrelation des unspezifisch permeablen mitochondrialen Raumes mit dem „Intermembran‐Raum”

Abstract

The term “unspecific permeability” in mitochondria is defined for describing a rapid equilibration of solutes between the extraamitochondrial space and a portion of the intramitochondrial space. It appears to be a property of the outer membrane and is restricted only by the size of the molecule (maximal molecular weight of 5,000–12,000). The unspecifically permeable space varies considerably. It ranges from 20–80% in different preparations of mitochondria. For a single mitochondrial preparation it is shown to be of equal volume for various small molecules such as sucrose, adenine nucleotides, NAD+ and aspartate. The total aqueous phase of rat liver mitochondria in isotonic sucrose medium ranges from 2.5–3.4 μl/mg protein; the aqueous part of the impermeable space from 0.8–1.8 μl/mg protein. Only about 1 μl of this portion expands osmotically and represents the solvent for endogenous mitochondrial solutes. The major part (about 0.4–0.6 μl/mg protein) of the residual water of the impermeable space may be attributed to the hydrate shell of mitochondrial protein. The unspecifically permeable and the impermeable space of the mitochondria are compared with the morphologically defined intermembrane and matrix space. The tonicity of the incubation medium was varied over a large range for rat liver and rat kidney mitochondria in order to facilitate this comparison. Large variations in the ratio of sucrose permeable to impermeable space (ranging from 1:3 in liver mitochondria to 3:1 in kidney mitochondria) correspond to changes in the ratio of the areas covered by the intermembrane and matrix space in the sections seen in the electron‐micrographs. Mitochondria with low unspecific permeability are homogenous, mitochondria with high unspecific permeability show greater individual variability at all tonicities. Copyright © 1968, Wiley Blackwell. All rights reserved