Regulation of cerebrospinal fluid bicarbonate by the cat choroid plexus.

Abstract

The regulation of CSF bicarbonate concentration was studied using the cat choroid plexus isolated in a chamber in situ. Decreases in plasma bicarbonate concentration caused relatively small changes in the CSF bicarbonate concentration. Alterations in CSF bicarbonate concentration (CSF HCO3- = 9 or 28 meq/l) were countered by changes in the bicarbonate concentration of the fluid produced by the plexus or in the rate of bicarbonate transport which returned CSF bicarbonate towards normal. There was significant regulation of pH in the choroid plexus fluid during hypocapnia and hypercapnia. Alterations of plasma acid-base status did not significantly alter the potential difference across the choroid plexus. However, the potential difference increased when CSF bicarbonate was increased and decreased when CSF bicarbonate was decreased. The bicarbonate concentration in the CFS was actively regulated by the Choroid plexus during acid-base disturbances occurring either systemically or in the CSF.