K-Na EXCHANGE ACCOMPANYING THE PROLYTIC LOSS OF K FROM HUMAN RED CELLS

In systems containing human red cells and sodium taurocholate as a lysin, or distearyl lecithin as a sphering agent, the prolytic loss of K at 25 degrees C. is accompanied by a gain of Na by the cell, the gain being somewhat greater than the K loss. A small volume increase accompanies the exchange. The kinetics of the K loss and the Na gain are similar to those already described; i.e., the changes are rapid at first, and slow down so that after 12 to 20 hours it appears that a new steady state is being approached. Similar, but smaller, losses of K and gains of Na occur when the cells stand in isotonic NaCl at 25 degrees C. without the addition of a lysin or sphering agent. On these and other experimental grounds, it is impossible to retain the idea that the mammalian red cell in general is impermeable to cations. The cells nevertheless seem to be in a steady state with respect to their environment, their ionic composition changing as the composition of the environment is changed. The possible processes by means of which one steady state can be exchanged for another-changes in the permeability of a surface membrane, changes in the velocity of an active ion transfer process dependent on red cell metabolism, and changes in the activity of the ions in the red cell interior as a result of changes in an orderly internal structure-are discussed.