Journal of Applied Physiology, Vol 51, Issue 2 369-375, Copyright © 1981 by American Physiological Society
Evidence of active regulation of cerebrospinal fluid acid-base balance
S. W. Bledsoe, D. Y. Eng and T. F. Hornbein
To test the passive transport hypothesis of cerebrospinal fluid (CSF) [H+]
regulation, we altered the relationship between plasma [H+] and the
electrical potential difference between CSF and blood (PD) by elevating
plasma [K+] during 6-h systemic acid-base disturbances. In five groups of
pentobarbital-anesthetized dogs, we increased plasma [K+] from 3.5 to an
average of 7.8 meq/l. Hyperkalemia produced an increase in the PD of 6.3 mV
by 6 h with normal plasma acid-base status (pHa 7.4), of 8.3 mV with
isocapnic metabolic acidosis (pHa 7.2), of 5.3 mV with isocapnic metabolic
alkalosis (pHa 7.6), of 9.2 mV with isobicarbonate respiratory acidosis
(PaCO2 61 Torr) and of 5.7 mV with isobicarbonate respiratory alkalosis
(PaCO2 25 Torr). The change in CSF [H+] at 6 h in each group was the same
as that observed in normokalemic animals (Am. J. Physiol. 228: 1134-1154,
1975). This result is not consistent with the passive transport hypothesis.
The CSF-blood PD is therefore not an important determinant of CSF [H+] CSF
[H+] homeostasis must result from some form of active transport control.
