Effects of Potassium On Concentrations of Ions and Proteins and OnPH In Brain-Cortex Slices from New-Born and Adult Rats

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Abstract
Sodium, potassium and chloride concentrations, protein content and intracellular pH (pH/) were measured in brain-cortex slices from new-born and adult rats incubated in ‘balanced’ or potassium-rich media. The following results were obtained: (1) After incubation in the ‘balanced’ medium the immature tissue shows a higher concentration of K+ (86.3 μmoles/g final wet wt.) and lower concentrations of Na+ (71.8 μmoles/g) and CI− (55.2 μmoles/g) than mature tissue. The protein anion concentration probably corresponds approximately to the anion deficit, which amounts to about 100 μeq./g in new-born and 80 μeq./g in adult animals; the protein concentration nevertheless shows an increase (from 98.2 mg to 133.7 mg/g final wet wt.) during maturation. pHt, remains unaltered at 6.95. (2) Addition of excess potassium evokes a decline of the deficit in monovalent anions in both mature and immature tissue. In the latter the decrease occurs continuously over the whole external potassium concentration range (5-85 mM), whereas it is confined to the interval 25-40 mM in mature brain. This abrupt decline in the brain slices from adult rats corresponds to a reduction of the protein content, and the pH, is not affected. In the brain slices from the new-born animals the continuous reduction of the deficit in monovalent anions is, in contrast, poorly reflected by the protein content, and pHt, shows a gradual reduction.