The Metabolism of Isolated Fat Cells

Abstract A method is described for the study of transport processes in ghosts isolated from rat adipose cells. With this procedure it was possible to follow the time course of potassium uptake, potassium release, and sodium release. The uptake of potassium was stimulated by sodium and was inhibited by ouabain at concentrations down to at least 10-6 m. In the presence of pyruvate (1 mm), potassium uptake showed a more rapid initial increase, and the steady state level was more than doubled. Glucose (5 mm) produced a smaller stimulation of potassium uptake. Cyanide, 2,4-dinitrophenol, or incubation in the cold diminished both potassium uptake and content. Potassium efflux, unlike uptake, was not altered by ouabain or pyruvate; a half-life of 45 min was found. Sodium ion was exchanged but not accumulated by ghosts. Efflux studies showed that sodium was released with a half-life of 10 min. It is concluded that potassium is accumulated by ghosts of fat cells via a sodium-linked, energy-requiring process characteristic of an intact plasma membrane.