Gravitational field enhances permeability of biological membranes to sucrose: an experimental refutation of sucrose-space hypothesis.

Isotonic conditions for the integrity of subcellular organelles are shown to be remarkably influenced by the concentration of sucrose present during their isolation by centrifugation. Using the technique of enzyme osmometry, we show that the content of sucrose in synaptosomes reflects nearly total equilibration across the membrane during centrifugation, due to altered permeability of membranes. Presence of sucrose in the matrix space of mitochondria, as demonstrated by enzyme osmometry of matrix enzymes, indicates that the sucrose-space hypothesis is invalid.