The permeation of non-electrolytes through the single barnacle muscle cell

The rate of movement of non-electrolytes and tritiated water (THO) across the muscle cell membrane of the giant barnacle Balanus nubilus has been studied and permeability coefficient calculated. The rate of permeation is more closely related to the oil-water partition coefficient than to size of the molecule or degree of hydrogen bonding. Calculations based on efflux from an ideal cylinder suggest that the membrane acts as a significant barrier to movement of these molecules. The cell was unable to concentrate dimethyl sulphoxide (DMSO); the steady state was reached at about 60% of the extracellular concentration. The energies of activation for water, urea and DMSO are 7.5, 20.3 and 26.1 kcal/mol. At 4 degrees C the apparent pore size measured with urea, glycerol and DMSO was 3.5 A. At 25 degrees C the apparent pore size for urea and glycerol is unchanged but that for DMSO is 14 A.