Effect of plasma [K+] on the DC potential and on ion distributions between CSF and blood.
Abstract:
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.
