Distribution of Sodium and Potassium in the Nucleus and Cytoplasm of Neurons

Abstract

Until recently, the assignment of distribution of ions to various compartments in the nervous system has been entirely dependent on kinetic, physiological measurements such as ‘sucrose space’ or ‘sulphate space’, with consequent poor degree of certainty regarding the correspondence of such measurements with particular cellular elements or even with the intracellular and extracellular compartments. Refinements in techniques of volume determination in tissue sections (Lehrer et al., 1970) as well as the development of techniques for measurement of sodium and potassium at high sensitivity (Katzman et al., 1969; Lehrer, 1971) and increasing ability for localization of diffusible molecules in sections (Lehrer, 1969) now permit far greater confidence in determination of intracellular and extracellular distributions of such small molecules. Unfortunately, these techniques do not give any information on state of ionization or chemical activity, but only elemental distribution.