Membrane permeability of isolated lung cells to nonelectrolytes

Mixtures of viable endothelial and epithelial cells were separated by enzymatic digestion from rabbit lung and recovered by centrifugation. The cells were mixed with an extracellular marker and packed by centrifugation into small-diameter polyethylene tubing and pulsed with tritiated water and 14C-labeled alcohols. Calculation of diffusion coefficients for the packed cell column (D), intracellular material (D2), and extracellular fluid (D1) was based on a local steady-state one-dimensional diffusional model. Permeability coefficients were: tritiated water, 288 X 10(-5) cm s-1; methanol, 385 X 10(-5) cm s-1; ethanol, 214 X 10(-5) cm s-1; propanol, 277 X 10(-5) cm s-1; and hexanol, 1255 X 10(-5) cm s-1. The permeability coefficients of these aliphatic alcohols show a minimum at ethanol with hexanol having the highest value of all substances tested. The results support the concept of parallel aqueous and lipid pathways for small solutes in the plasma membrane. Study of the permeability properties of isolated lung cells can provide information on the cellular pathway in the transcapillary transport of water and solutes in the lung.