Epithelial Pathways in Choroid Plexus Electrolyte Transport

Abstract

A stable intraventricular milieu is crucial for maintaining normal neuronal function. The choroid plexus epithelium produces the cerebrospinal fluid and in doing so influences the chemical composition of the interstitial fluid of the brain. Here, we review the molecular pathways involved in transport of the electrolytes Na+, K+, Cl-, and HCO3(-)across the choroid plexus epithelium.

Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase II enhances CO2 fluxes across Xenopus oocyte plasma membranes

“…These processes include CO 2 carriage by erythrocytes (42), HCO 3 Ϫ transport across epithelia (11,21,36,53,54), fluid transport across epithelia (2,18,35,40,53,62), transient changes in extracellular pH in the brain (12), and the speed of certain intracellular pH transients (58,71). For a particular animal species, the enzymatically active ␣-CAs differ in catalytic activity, affinity for CO 2 , inhibitor sensitivity, and expression pattern (32,54,65).…”

Severe Neurologic Impairment in Mice with Targeted Disruption of the Electrogenic Sodium Bicarbonate Cotransporter NBCe2 (Slc4a5 Gene)

“…The process of CSF transepithelial ion and fluid secretion involves an array of transporters and channels (6,15). Fluid secretion is dependent on the active transepithelial transport of Na ϩ mediated by an apical Na ϩ -K ϩ -ATPase pump, carbonic anhydrase activity, basolateral sodium bicarbonate influx mediated by the SLC4 transporter NCBE, and water transfer across the apical membrane via aquaporin 1.…”

“…Fluid secretion is dependent on the active transepithelial transport of Na ϩ mediated by an apical Na ϩ -K ϩ -ATPase pump, carbonic anhydrase activity, basolateral sodium bicarbonate influx mediated by the SLC4 transporter NCBE, and water transfer across the apical membrane via aquaporin 1. Additional ion transporters are expressed in CPE cells, including NBCn1, AE2, NHE1, Clir channels, NBCe2, VRAC, and NKCC1, which are also thought to play a role in CSF production (15).…”

KCNE2 and the K+channel

“…48,49 Accordingly, the flux of ions from the basolateral (blood) side to the apical (CSF) side of the CPe must be exquisitely regulated, as it is highly influential upon physiological aspects of the CNS including neuronal function and intracranial pressure [50][51][52][53] (Fig. 2B).…”