Cocompartmentation of proteins and K+ within the living cell.

Monolayer H-50 tissue culture cells were treated with Triton X-100 and Brij 58 nonionic detergents, and their electron microscopic morphology along with the release of the intracellular proteins and K+ were studied. Although Triton X-100 was more effective, both detergents removed the lipoid membranes within 5 min. The mobilization and solubilization of the cytoplasmic and nuclear proteins occurred much faster with Triton X-100 than with Brij 58. In Triton X-100-treated cells, the loss of K+ was complete within 2 min. The loss of K+ from the Brij 58-treated cells was complete only after 10 min and the mobilization of K+ showed sigmoid-type release kinetics. These results support the view that most of K+ and "diffusible" proteins not freely dissolved in the cellular water, but they are cocompartmentalized inside the living cell.