The osmotic permeability coefficient for water has been measured for the Ehrlich mouse ascites tumor cell. Measurements were made of the rate of cell shrinkage in hyperosmotic solutions of NaCI, a functionally impermeable solute. During the first 9 months of weekly serial transplantation the mean was 6.4/~8//~2/atm. 4-0.8 (S.E.). By the end of the 2nd year the permeability coefficient was much lower and averaged 1.6 4-0.09. There were no significant differences in the volume of the tumor cells which could explain the discrepancy on the basis of a change in the volume to surface area ratio. Studies of the effect of temperature were done and Eyring's theory of absolute reaction rates was applied to the data. The apparent energy of activation was 9.6 kcal./mol and AS~ was 39.1 entropy units. The thermodynamic data are twice as high as data reported by Wang for self-diffusion and viscous properties of water. Two alternate explanations have been advanced based on the pore hypothesis of membrane permeability. One explains the thermodynamic data from a change in the A ' / A x available for water movement; the other assumes A ' / A x constant and bases the results on the interaction of water dipoles with each other and the membrane. I N T R O D U C T I O NA characteristic of the neoplastic cell is its ability to c o m p e t e successfully with the host tissues for a limited supply of nutrients. This is especially so for the rapidly growing tumors where the energy d e m a n d s m a y be considerable. Since the m e m b r a n e of the t u m o r cell is the first barrier which the cell shows to its environment, a functional description of this barrier will serve to elucidate the means by which the cell can regulate the constituents which enter or leave the cell. This r e p o r t on the permeability characteristics of the Ehrlich ascites t u m o r cell to water deals with one aspect of the p r o b l e m of t u m o r cell p e r m e ability.

We have measured the equilibrium efflux of CI4 labeled glucose across the cell membrane of the human erythrocyte under conditions when glucose was present in equal concentrations on both sides of the cell membrane, and also the net efflux of Ci4 labeled glucose from glucose-loaded cells into a large extracellular environment that contained no glucose. A method of ultrafiltration through millipore filter discs was developed to obtain samples of medium during the loss of cell isotope to a medium free of isotope. Fluxes with half times as low as five seconds could be determined accurately and reproducibly. With this method we have extended the observations of other workers down to glucose concentrations of 0.03 M and found as others had previously that the half time for tracer exchange would decrease with a decrease in the equilibrium glucose concentrations. Further, by measuring equilibrium fluxes and maximal net fluxes of cells from the same blood sample, we have obtained evidence that the carrier laden with glucose is transported more rapidly than the free carrier.

The osmotic properties of human lymphocytes isolated from 15 ml of venous blood were examined. Measurements of the permeability of the membrane to water under an osmotic gradient were also made. The Boyle-Van't Hoff relation held very well for the human lymphocyte when the cells were shrunken in hyperosmotic media to concentrations twice isosmotic. The volume of osmotically inactive material or "b" value averaged 32% of the mean corpuscular volume. These values were independent of temperature. Ponder's R ranged between 0.8 and 0.9. The average value for Lp, the hydralic coefficient was 0.46 mu/min atm +/- 0.02 (S.E.M.) at 25 degrees C. No significant effect of age, sex, or race was noted. The effect of temperature between 10 degrees C and 37 degrees C was measured and heats of activation between 11.1 and 17.4 kcal/mole were calculated with a mean of 14.1 kcal/mole +/- 1.6 (S.E.M.). Concanavalin A at 10 microgram/1.5 X 10(6) lymphocytes produced blastogenesis of 25% or more of the lymphocytes without clumping, agglutination, or toxicity. The mean corpuscular volume increased by 21% after 72 hours due to an increase in the "b" value which increased by 80%. The volume of free water remained constant. Histograms of the distribution of cell volumes showed that volume changes were uniform throughout the population with no evidence of agglutination of clumping. The significance of these results is discussed in the context of membrane fluidity and the state of intracellular water.