Stability of the potassium content of cerebrospinal fluid and brain

Abstract

Rabbits were depleted of potassium by the feeding of an artificial diet free of potassium salts. At 3 weeks, when the plasma potassium had fallen to between 1 and 2 mEqAiter, CSF [cerebrospinal fluid] and brain potassium were almost unchanged; muscle potassium fell to less than two-thirds of its control value. Plasma potassium was raised to between 6 and 8 mEqAiter by feeding a high-potassium diet. Muscle potassium per unit wet weight was unchanged but increased by 8% per unit dry weight. CSF potassium increased minimally and brain potassium not at all. The potential between ventricular CSF and jugular venous blood was 3-6 mv (CSF positive) and increased slightly at high plasma potassium levels. Potassium influx into brain, measured with 42K, comprised 2 components; one was constant and independent of the plasma potassium, the other varied directly with it. Stability of brain and CSF potassium is, in part, affected by a control of influx, but there must be also enhancement of outflux at increasing plasma potassium concentrations.