title: Adenine nucleotides in cholinergic transmission: presynaptic aspects.
abstract: 1. Isolated nerve terminals (T-sacs and synaptosomes) prepared from the purely cholinergic Torpedo electric organ have been studied for their ability to incorporate and metabolise [2-3H] adenosine and to degrade 5'-AMP to adenosine. 2. A temperature-dependent, saturable uptake system for adenosine was found with kinetic properties similar to nucleoside transport systems in other cells. The uptake system in Torpedo nerve terminals was inhibited by 2'-deoxyadenosine, a known inhibitor of adenosine transport. 3. Intraterminal adenosine is rapidly metabolised to a number of products including AMP, ADP and ATP. 4. Isolated nerve terminals contain considerable 5'-nucleotidase activity, most of which resides on the outer face of the external membrane. The Km of the enzyme is congruent to 5 micron and it is inhibited by a phosphonate analogue of ADP, alpha-beta-methylene-ADP. It is suggested that this 5'-nucleotidase plays an important role in the production of adenosine from a nucleotide pool in the synaptic cleft.
mesh_terms: D000227:Adenine Nucleotides / Q000502:physiology*; D000241:Adenosine / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D002799:Cholinergic Fibers / Q000502:physiology; D004557:Electric Organ / Q000294:innervation / Q000502:physiology*; D005399:Fishes; D009411:Nerve Endings / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000502:physiology; D009708:Nucleotidases / Q000378:metabolism; D009435:Synaptic Transmission; D013574:Synaptosomes / Q000378:metabolism
chemical_list: D000227:Adenine Nucleotides; D009708:Nucleotidases; D000241:Adenosine