Sodium fluxes in isolated frog brain

¹ Institute of Biological Chemistry, University of Copenhagen, Copenhagen, Denmark

The properties of a preparation of isolated frog brain bathed in a Ringer's solution have been examined in order to determine whether it is suitable for study of ion movements. The preparation can be maintained in a steady state with respect to Na and water content for up to 5 hr. Under our conditions the washout of Na²⁴ from preloaded brains appears to be made up of two components, a fast one having a half time of 7.4 min and a slow one having a half time of 54.6 min. The slow component of washout was affected by ouabain, iodoacetate, and cyanide and by reduced temperature, and appears to represent a cellular compartment. The fast component was not affected by metabolic poisons and appears to represent an extracellular space making up approximately 24% of the wet weight of the tissue. The effective diffusion coefficient of Na in this space was found to be 0.82 x 10^–5 cm²/sec. A method of calculating Na fluxes from the data on Na²⁴ washout is discussed.

Key Words: extracellular space • ion movements • metabolic poisons • cellular compartments

Submitted on May 6, 1963