Whole cell Cl- conductances in mouse choroid plexus epithelial cells do not require CFTR expression
Kibble, J.D.; Garner, C.; Colledge, W.H.; Brown, S.; Kajita, H.; Evans, M.; Brown, P.D.
American Journal of Physiology 272(6 Pt 1): C1899-C1907
1997
ISSN/ISBN: 0002-9513 PMID: 9227419 Document Number: 470558
Whole cell patch-clamp studies were performed with tissue isolated from the cystic fibrosis (CF) transgenic Cftr-m1cam mouse, to determine whether anion currents in choroid plexus epithelial cells require the expression of cystic fibrosis transmembrane conductance regulator (CFTR). Inclusion of 0.25 mM adenosine 3',5'-cyclic monophosphate (cAMP) and 375 nM protein kinase A (PKA) in the pipette solution caused a significant activation of a Cl--selective, inward-rectifying conductance in cells from wild-type and CF mice. The small, outward currents observed in wild-type and CF animals, however, were not activated by cAMP-PKA. There were no significant differences in the size of currents between wild-type, heterozygote, and CF cells in the presence or absence of cAMP-PKA. A second whole cell conductance was activated when cells from wild-type mice were swollen. These volume-activated currents were Cl- selective and exhibited outward rectification. They were Ca-2+ independent and ATP dependent and blocked by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and 5-nitro-2-(3-phenylpropylamino)benzoic acid. The volume-activated channels were also activated in CF mutant cells, and there was no significant difference in the size of the volume-activated currents between wild-type, heterozygote, and CF cells. It is concluded that CFTR neither contributes to the whole cell conductance nor regulates the other anion conductances in choroid plexus epithelial cells.