Potassium exchange between cerebrospinal fluid, plasma, and brain

¹ Department of Physiology, Harvard Medical School, Boston, Massachusetts

Potassium exchange between cerebrospinal fluid (CSF), plasma, and brain was investigated in anesthetized dogs and rats using the technique of ventriculocisternal perfusion. Transport via bulk secretion and absorption of CSF accounts for only 20% of total potassium exchange, unidirectional ionic fluxes across the ependyma for 80%. This large transependymal exchange is primarily between CSF and brain intracellular potassium pools, since two-thirds of the K⁴² outflux can be recovered from brain tissue. Conversely, much of transependymal influx comes from brain, as demonstrated by the low specific activity of influx relative to that of plasma following intravenous injection of K⁴². Potassium outflux is almost proportional to CSF [K⁺] in the range 0–10 mEq/liter but is independent of plasma [K⁺]. Perfusion with 10^–5 m ouabain reduces transependymal K⁴² outflux to 25% of control; the residual outflux may be accounted for by passive processes. Results are discussed in terms of 1) regulation of CSF potassium concentration and 2) the relationship between CSF and brain extracellular fluid.

Key Words: CSF potassium • blood-brain barrier • ependyma • ouabain • acetazolamide • extracellular fluid of brain • choroid plexus

Submitted on May 19, 1965

This article has been cited by other articles:

				H. Kager, W. J. Wadman, and G. G. Somjen Conditions for the Triggering of Spreading Depression Studied With Computer Simulations J Neurophysiol, November 1, 2002; 88(5): 2700 - 2712. [Abstract] [Full Text] [PDF]

				G. Chen, W. L. Castro, H.-H. Chow, and S. Reichlin Clearance of 125I-Labeled Interleukin-6 from Brain into Blood Following Intracerebroventricular Injection in Rats Endocrinology, November 1, 1997; 138(11): 4830 - 4836. [Abstract] [Full Text] [PDF]

				A. C. Mancall, G. J. DiGregorio, C. B. Brill, and E. Ruch The Effect of {bigtriangleup}-9-Tetrahydrocannabinol on Rat Cerebrospinal Fluid Arch Neurol, November 1, 1985; 42(11): 1069 - 1071. [Abstract] [PDF]

				H. S. Kirshner, W. F. Blank Jr, and R. E. Myers Changes in Cortical Subarachnoid Fluid Potassium Concentrations During Hypoxia Arch Neurol, February 1, 1976; 33(2): 84 - 90. [Abstract] [PDF]