DETERMINATION OF VOLUME AND WATER PERMEABILITY OF PLATED CELLS FROM MEASUREMENTS OF LIGHT-SCATTERING

Measurements of cell membrane water osmotic permeabilities can be inac curate because of the technical difficulties inherent to cell volume m easurements and because of the presence of an unstirred water layer in contact with the cells. We detail here a method we have developed to quantify transient changes in cell volumes from the intensity of light scattered by cells. For this, we theorize how an unstirred layer orig inates in a perfusing chamber, and we calculate values for both cell m embrane water osmotic permeability and unstirred layer thickness from time transient changes in scattered light. We apply a computer algorit hm that finds the best correspondence between experimental data and es timated values. This is done by solving a differential equation govern ing cell volume changes by numerical integration (Runge-Kutta) and ite rating the procedure varying the test values of osmotic permeability a nd unstirred layer thickness until the best fit is achieved. We exempl ify this procedure with experimental results obtained in adherent cult ured cells.