title: Choline: high-affinity uptake by rat brain synaptosomes.
abstract: Synaptosomes from rat brain accumulate choline by two kinetically distinct processes, a high-affinity uptake system [Michaelis constant (K(m)) = 1 x 10(-6)M], and a low-affinity system (K(m) = 9 x 10(-5)M). The high-affinity uptake system requires sodium, and is associated with considerable formation of acetylcholine. The low-affinity uptake system is less dependent on sodium, and does not appear to be associated with a marked degree of acetylcholine formation. The high-affinity choline uptake appears to represent selective choline accumulation by cholinergic neurons.
mesh_terms: D000109:Acetylcholine / Q000032:analysis; D000818:Animals; D001479:Basal Ganglia / Q000378:metabolism*; D001622:Betaine / Q000032:analysis; D001923:Brain Chemistry; D002794:Choline / Q000032:analysis / Q000378:metabolism*; D003342:Corpus Striatum / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009411:Nerve Endings / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D010758:Phosphorus / Q000032:analysis; D051381:Rats; D012964:Sodium / Q000494:pharmacology; D013572:Synaptic Vesicles / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D014316:Tritium
chemical_list: D014316:Tritium; D010758:Phosphorus; D001622:Betaine; D010042:Ouabain; D012964:Sodium; D002794:Choline; D000109:Acetylcholine