Ammonia-induced alterations in the activities of synaptosomal cholinesterases of rat brain under in vitro and in vivo conditions.
Effects of in vivo and in vitro pathophysiological concentrations of ammonium acetate were studied on the activities of acetyl and pseudocholinesterases in the synaptosomes isolated from cerebral cortex, cerebellum and brain stem of rat brain. Administration of subacute and acute doses of ammonium acetate elevated the activities of both the cholinesterases in synaptosomes of all the above three regions. A linear relationship (r = 0.98) was observed between brain-ammonia levels and magnitude of elevation in the activities of cerebral cholinesterases. Kinetic analysis revealed that this elevation was due to a change in the Vm but not in the Km of the enzymes. Incubation of synaptosomes isolated from normal animals with 1, 5 and 10 mM ammonium acetate marginally elevated the activities of these enzymes and had no effects on purified enzyme. It is suggested that the changes in the activities might be due to altered architecture of the membranes which exposes more number of catalytic sites.
Devi
R P
RP
Department of Animal Sciences, School of Life Sciences, University of Hyderabad, India.
Murthy
C R
CR
D000110:Acetylcholinesterase / Q000097:blood / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects; D002091:Butyrylcholinesterase / Q000097:blood / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002802:Cholinesterases / Q000097:blood / Q000378:metabolism*; D007274:Injections, Intraperitoneal; D007700:Kinetics; D051381:Rats; D017208:Rats, Wistar; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology*
D000641:Ammonia; D000110:Acetylcholinesterase; D002091:Butyrylcholinesterase; D002802:Cholinesterases