Aquaporin-1 deletion reduces osmotic water permeability and cerebrospinal fluid production.
Aquaporin-1 (AQP1) is a water channel that is strongly expressed at the ventricular-facing surface of choroid plexus epithelium. Using wildtype and AQP1 null mice, we developed novel methods to compare the water permeability in isolated choroid plexus, and cerebrospinal fluid (CSF) production in living mice. Osmotically-induced water transport was rapid in freshly isolated choroid plexus from wildtype mice as measured by a spatial-filtering optical method, and reduced by 5-fold by AQP1 deletion. CSF production, an isosmolar fluid secretion process, was measured by a dye dilution method involving fluid collections using a second microneedle introduced into the cisterna magna. CSF production in wildtype mice was (in microl/min) 0.37 +/- 0.04 microl/min (control), 0.16 +/- 0.03 microl/min (acetazolamide-treated) and 1.14 +/- 0.15 microl/min (forskolin-treated), and reduced by up to 25% in AQP1 null mice. The impaired CSF production in AQP1 null mice provides direct functional evidence for the involvement of AQP1 in CSF formation.
T10 T11 T1 T2 T3 T4 T5 T6 T7 T8 T9
GENE-Y GENE-Y CHEMICAL CHEMICAL GENE-Y GENE-Y GENE-Y GENE-Y GENE-N GENE-Y GENE-Y
AQP1 Aquaporin-1 acetazolamide forskolin Aquaporin-1 AQP1 AQP1 AQP1 water channel AQP1 AQP1