Table 6.
Comparison of brain microvascular endothelial cell transport and transporters with those of choroid plexus epithelium and corneal endothelium (corneal posterior epithelium). Results from this study are in bold
| Transport activity | Brain microvascular endothelial cells | Choroid plexus | Corneal endothelium |
|---|---|---|---|
| Basal pH with HCO3− | 7.151, 6.92 | 7.38 | 7.151, 7.372 |
| Na+/H+ exchanger | Functional at pH 7.11 | NHE1 (mRNA)1 | Functional1,2 |
| Functional at acid pH1,2 | |||
| NHE1 (mRNA)1 | |||
| NHE1 binding assay3 | |||
| NHE1-4 (mRNA)2 | |||
| Na+-dependent, | Functional at pH 7.1 (presumed apical)1 | NBCe2(ap)2 | Functional1,3,4 |
| Cl− independent | NBCe1 (mRNA)1 | NBCn1 (bl)3 | bl5 |
| HCO3− influx | NBCn1 (mRNA)1 | NBCe15,6,7 | |
| Na+ dependent, | Transport at acid pH2 | NCBE# (bl)3 | |
| Cl− dependent | NCBE# (mRNA)1 | ||
| HCO3− influx | NDBCE (mRNA)1 | ||
| Na+-independent Cl−/HCO3− exchange | Functional1 | AE2 (bl)4,5,6 | Functional1,4 |
| AE2 (mRNA)1 | ProbablyAE2 (bl)5 | ||
| Na+,K+-ATPase | bl4 | ap7,8 | bl8 |
| Na+−K+−2Cl− cotransport | ap5 | ap6 | bl5,9 |
| Net transport | ap (blood) to bl (brain interstitial fluid) | bl (blood) to ap (CSF) | bl (corneal stroma) to ap (aqueous humour) |
| Secretory function | Secretion of brain | Secretion of CSF | Maintenance of osmotic pressure difference to oppose stromal swelling pressure |
| Interstitial fluid | |||
| Embryological origin | Mesoderm6 | Neural tube | Neural crest10 |
| References | 1. This study | 1. Kalaria et al. (1998) | 1. Jentsch et al. (1988) |
| 2. Sipos 2005 | 2. Bouzinova et al. (2005); | 2. Bonanno & Giasson (1992a) | |
| 3. Kalaria et al. (1998) | 3. Praetorius et al. (2004b) | 3. Jentsch (1984) | |
| 4. Betz et al. (1980); Betz (1983) | 4. Lindsey et al. (1990) | 4. Bonanno & Giasson (1992b) | |
| 5. O'Donnell et al. (2004) | 5. Alper et al. (1994) | 5. Bonanno (2003) | |
| 6. Gage et al. (2005) | 6. Wu et al. (1998) | 6. Li et al. (2005) | |
| 7. Mazusawa et al. (1984) | 7. Usui et al. (1999) | ||
| 8. Ernst et al. (1986) | 8. Guggenheim & Hodson (1994) | ||
| Reviews: Brown et al. (2004) and Praetorius & Nelson (2006) | 9. Jelamskii et al. (2000) | ||
| 10. Gage et al. (2005) |
ap, apical; bl, basolateral. #The Cl− dependence of NCBE remains controversial; see Wang et al. (2000), Choi et al. 2002 and Romero et al. (2004). The assignment adopted here follows that of Bouzinova et al. (2005) and Praetorius & Nielsen 2006.