Potassium retention in membraneless thymus lymphocyte nuclei.

Nonionic detergents, Triton X-100 and Brij 58, removed lipoid membranes of suspended thymus lymphocytes within 5 minutes. The mobilization and solubilization of cytoplasmic and nuclear proteins occurred much faster (less than 5 minutes) with Triton X-100 treatment than with Brij 58 treatment (less than 10 minutes). In Triton X-100 treated cells the loss of K+ was complete within 5 minutes whereas with Brij 58 treatment the K+ loss was not complete after 10 minutes. Thus, the high concentration of K+ and the low concentration of Na+ in the nuclei can remain near normal for minutes in the absence of membrane structures. If the ions were in free solution within the cells, disruption of membrane integrity should lead to equilibration of the ions with external media within seconds. The decrease of K+ in the Brij 58 treated cells with exposure time was correlated with the solubilization of the proteins. These results support the view that K+ and Na+ are not freely dissolved in the cellular water, but are co-compartmentalized with proteins inside the living cell.