Estimation of Ionic Concentrations and Intracellular pH in Slices from Different Areas of Rat Brain

Tissue spaces occupied by 14 C‐sucrose and 3 H‐inulin were measured at different incubation time intervals (15–120 min) in rat brain slices prepared from cortex, cerebellum, caudate, diencephalon and midbrain. Total water content, total Na + and K contents and 14 C‐DMO (5,5‐dimethyl‐2,4‐oxaolidinedione) spaces were obtained from the same tissues. At all time intervals, 14 C‐sucrose spaces were larger than corresponding 3 H‐inulin spaces. After 60 min incubation, the mean values for 14 C‐sucrose spaces in preparations from different brain areas ranged from 31.5 to 38.1 m1/100 g, whereas the 3 H‐inulin space mean values were 19.3–26.1 m1/100 g. Average intracellular pH was calculated from 14 C‐DMO spares in the presence and absence of 3.67 mM procaine. The pH 1 values obtained using inulin‐derived extracellular spares were 6.91–6.99, and those calculated from sucrose spaces were 6.77–6.89. The contents of K + and Na + showed no distinct regional differences, but a potassium uptake with time could only be observed in preparations from cerebral and cerebellar cortex.