title: Cooperative effects of hemicholinium-3 on high-affinity choline uptake by rat diaphragm.
abstract: Choline uptake in the end-plate rich area of rat diaphragm is saturable between 0.7 and 16 micron. This choline uptake obeys hyperbolic kinetics and indicates the presence of high-affinity carrier with Km values of 11.8 and 13.2 micron and Vmax values of 37 and 31 nmol choline/h/g tissue respectively. In the presence of hemicholinium-3 the carrier shows sigmoidal kinetics, and hemicholinium-3 is apparently a cooperative effector of choline uptake. The carrier is more calcium than sodium dependent.
mesh_terms: D000818:Animals; D002794:Choline / Q000378:metabolism*; D003964:Diaphragm / Q000378:metabolism; D005260:Female; D006426:Hemicholinium 3 / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D009045:Motor Endplate / Q000378:metabolism; D009132:Muscles / Q000378:metabolism*; D051381:Rats
chemical_list: D006426:Hemicholinium 3; D002794:Choline