Choline uptake across the ventricular membrane of neonate rat choroid plexus.
The uptake of [3H]choline from the cerebrospinal fluid (CSF) side of the rat neonatal choroid plexus was characterized in primary cultures of the choroidal epithelium grown on solid supports. Cell-to-medium concentration ratios were approximately 5 at 1 min and as high as 70 at 30 min. Apical choline uptake was facilitated; the Km was approximately 50 microM. Several organic cations (e.g., hemicholinium-3 and N1-methylnicotinamide) inhibited uptake. The reduction or removal of external Na+ or the addition of 5 mM LiCl had no effect on uptake. However, increasing external K+ concentration from 3 to 30 mM depolarized ventricular membrane potential (-70 to -15 mV) and reduced uptake to 45% of that for the control. Treatment with 1 mM ouabain or 2 mM BaCl2 reduced uptake 45%, and intracellular acidification reduced uptake to approximately 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 to Na+ influx but is sensitive to plasma membrane electrical potential.
Villalobos
A R
AR
Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269, USA. villalobos@oracle.pnb.uconn.edu
Parmelee
J T
JT
Renfro
J L
JL
D000143:Acids / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D002412:Cations / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002552:Cerebral Ventricles / Q000378:metabolism*; D002794:Choline / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics*; D002831:Choroid Plexus / Q000166:cytology / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008566:Membranes / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000494:pharmacology; D013237:Stereoisomerism; D013997:Time Factors
D000143:Acids; D002412:Cations; D012964:Sodium; D002794:Choline; D011188:Potassium