Osmotic permeability of Novikoff hepatoma cells

The osmotic permeability coefficient (Pf) for water movement across Novikoff hepatoma cells was found to be 82 +/- 3 (S.E.) x 10(-5) cm . s-1 at 20 degrees C. The corresponding diffusional permeability coefficient for 3HHO (Pd) was 97 +/- 10 (S.E.) . 10(-5) cm . s-1, therefore the ratio Pf/Pd is close to unity. The apparent activation energy for water filtration was 10.4 +/- 0.4 (S.E.) kcal . mol-1. This value is significantly greater than the activation energy for the self diffusion of water. The product of the hydraulic permeability coefficient and the viscosity coefficient for water was temperature-dependent. However, the product of the hydraulic permeability coefficient and the viscosity coefficient for membrane lipid did not vary with temperature. These data are interpreted as evidence for water movement across a lipid membrane barrier rather than through aqueous channels.