Inward-rectifying anion channels are expressed in the epithelial cells of choroid plexus isolated from ClC-2 'knock-out' mice.
Choroid plexus epithelial cells express inward-rectifying anion channels which have a high HCO(3)(-) permeability. These channels are thought to have an important role in the secretion of cerebrospinal fluid. The possible relationship between these channels and the ClC-2 Cl(-) channel was investigated in the present study. RT-PCR, using specific ClC-2 primers, amplified a 238 bp fragment of mRNA from rat choroid plexus, which was 99 % identical to the 5' sequence of rat ClC-2. A 2005 bp clone was isolated from a rat choroid plexus cDNA library using a probe for ClC-2. The clone showed greater than 99 % identity with the sequence of rat ClC-2. Inward-rectifying anion channels were observed in whole-cell recordings of choroid plexus epithelial cells isolated from ClC-2 knock-out mice. The mean inward conductance was 19.6 plus minus 3.6 nS (n = 8) in controls (3 heterozygote animals), and 22.5 plus minus 3.1 nS (n = 10) in three knock-out animals. The relative permeability of the conductances to I(-) and Cl(-) (P(I) : P(Cl)) was determined. I(-) was more permeant than Cl(-) in both heterozygotes (P(I):P(Cl) = 4.0 +/- 0.9, n = 3) and knock-out animals (P(I) : P(Cl) = 4.1 +/- 1.4, n = 3). These results indicate that rat choroid plexus expresses the ClC-2 variant that was originally reported in other tissues. ClC-2 does not contribute significantly to inward-rectifying anion conductance in mouse choroid plexus, which must therefore express a novel inward-rectifying anion channel.
Speake
Tracey
T
School of Biological Sciences, University of Manchester, Manchester M13 9PT, UK.
Kajita
Hidetoshi
H
Smith
Craig P
CP
Brown
Peter D
PD
D000465:Algorithms; D000818:Animals; D000838:Anions / Q000378:metabolism; D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels / Q000235:genetics* / Q000378:metabolism*; D002831:Choroid Plexus / Q000378:metabolism*; D004594:Electrophysiology; D004847:Epithelial Cells / Q000378:metabolism*; D015723:Gene Library; D066298:In Vitro Techniques; D007473:Ion Channels / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation / Q000235:genetics / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley
D000838:Anions; D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D007473:Ion Channels