Figure 28.

Role of NCBTs in the choroid plexus. The secretion of cerebrospinal fluid by the choroid plexus (CP) and intracellular pH regulation in CP epithelia is achieved by a combination of NCBTs. NBCe2 is the major NCBT that is responsible for HCO₃⁻ secretion across the apical membrane. NBCn1, NDCBE, and NBCn2 have all been detected in the basolateral membrane of CP epithelia, mediating HCO₃⁻ influx. NBCn1 has also been detected in the apical membrane of the CP in some strains of mice. Note that NDCBE is not present in the CP of adults. Reported, but not shown, is the presence of NBCe1 in the basolateral membrane.