Motional characteristics of K+ and Na+ in intact and sucrose-permeabilized rat lymphocytes.

Most, if not all, cells maintain an unequal distribution of Na+ and K+ against their environment. These two monovalent ions are in constant exchange between the cell and the extracellular space since both ions have proved to be permeable through the cell membrane. The distribution of Na+ and K+ in intact and "sucrose-permeabilized" rat lymphocytes were studied ("sucrose-permeabilization" means homogenization in isotonic sucrose solution). Both the intact and the permeabilized lymphocytes were incubated in Hanks' solution and then transferred into K+, Na(+)-free isotonic sucrose solution. Alternatively, the cells were incubated only in the sucrose solution or in Hanks' solution. The Na+ and K+ content of the cells were determined at the conclusion of each period of incubation in the same or different medium. We found that K+ did not equilibrate under any conditions in intact lymphocytes but Na+ responded to changes of the incubation media. In the permeabilized cells Na+ freely equilibrated with the extracellular medium while K+ did not, although its concentration decreased compared to that of intact cells.