CHARACTERIZATION OF HIGH AFFINITY CHOLINE UPTAKE BY TORPEDO CALIFORNICA T‐SACS

Abstract
Abstract— The high affinity choline uptake system present in T‐sacs prepared from Torpedo californica electric organ was shown to be insensitive to external Ca2+ and to be absolutely dependent on external NaCl, with optimal uptake at approx 200 mM‐NaCl. Both Na+ and Cl separately stimulate uptake. Uptake also exhibited an optimum at approx 10mM‐external K+. Uptake was completely inhibited at 4°C. Approximately 50% of newly accumulated [3H]choline was released by depolarization of T‐sacs regardless of the time or method of depolarization.