Journal of Applied Physiology, Vol 39, Issue 6 1012-1016, Copyright © 1975 by American Physiological Society
Effect of plasma [K+] on the DC potential and on ion distributions between CSF and blood
S. W. Bledsoe and A. H. Mines
Keeping the arterial pH at 7.4 and PaCO2 at 40 mmHg in eight anesthetized
dogs, we acutely raised plasma potassium concentration from 3.4 to 8.2
meq/1, then allowed it to decay back to control levels. The cerebrospinal
fluid (CSF)-blood electrical potential difference (pd) increased 13.2 mV
per 10-fold increase in plasma [K+]. Again keeping arterial pH at 7.4 and
PaCO2 at 40 mmHg, we elevated plasma [K+] in four dogs from 3.3 to 8.0
meq/1 and maintained this level for 6 h. We found 1) that the PD increased
from a control value of +1.3 to +8.9mV, showing no tendency to decay over
the 6 h; and 2) that the change in PD did not affect the distribution of
Na+, K+, H+, Cl-, or HCO3- between blood and CSF over the 6 h. These
results suggest that under these conditions the PD between CSF and blood
may play no effective role in determining the distributions of these
charged species by 6 h. These results are contrasted with recent findings
which suggest that H+ and HCO3- are distributed according to passive forces
between CSF and blood.
