Choline uptake across the ventricular membrane of neonate rat choroid plexus |
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Authors: | Villalobos, Alice R. Parmelee, Judith T. Renfro, J. Larry |
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Abstract: | The uptake of[3H]choline from thecerebrospinal fluid (CSF) side of the rat neonatal choroid plexus wascharacterized in primary cultures of the choroidal epithelium grown onsolid supports. Cell-to-medium concentration ratios were ~5 at 1 minand as high as 70 at 30 min. Apical choline uptake was facilitated; theKm was ~50µM. Several organic cations (e.g., hemicholinium-3 and N1-methylnicotinamide)inhibited uptake. The reduction or removal of externalNa+ or the addition of 5 mM LiClhad no effect on uptake. However, increasing externalK+ concentration from 3 to 30 mMdepolarized ventricular membrane potential (70 to 15 mV)and reduced uptake to 45% of that for the control. Treatment with 1 mMouabain or 2 mM BaCl2 reduced uptake 45%, and intracellular acidification reduced uptake to ~90%of that for controls. These data indicate that the uptake of choline from CSF across the ventricular membrane of the neonatal choroidal epithelium is not directly coupled toNa+ influx but is sensitive toplasma membrane electrical potential. |
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