Evidence that acute taurine treatment alters extracellular AMP hydrolysis and adenosine deaminase activity in zebrafish brain membranes.
Taurine is one of the most abundant free amino acids in excitable tissues. In the brain, extracellular taurine may act as an inhibitory neurotransmitter, neuromodulator, and neuroprotector. Nucleotides are ubiquitous signaling molecules that play crucial roles for brain function. The inactivation of nucleotide-mediated signaling is controlled by ectonucleotidases, which include the nucleoside triphosphate diphosphohydrolase (NTPDase) family and ecto-5'-nucleotidase. These enzymes hydrolyze ATP/GTP to adenosine/guanosine, which exert a modulatory role controlling several neurotransmitter systems. The nucleoside adenosine can be inactivated in extracellular or intracellular milieu by adenosine deaminase (ADA). In this report, we tested whether acute taurine treatment at supra-physiological concentrations alters NTPDase, ecto-5'-nucleotidase, and ADA activities in zebrafish brain. Fish were treated with 42, 150, and 400 mg L(-1) taurine for 1h, the brains were dissected and the enzyme assays were performed. Although the NTPDase activities were not altered, 150 and 400 mg L(-1) taurine increased AMP hydrolysis (128 and 153%, respectively) in zebrafish brain membranes and significantly decreased ecto-ADA activity (29 and 38%, respectively). In vitro assays demonstrated that taurine did not change AMP hydrolysis, whereas it promoted a significant decrease in ecto-ADA activity at 150 and 400 mg L(-1) (24 and 26%, respectively). Altogether, our data provide the first evidence that taurine exposure modulates the ecto-enzymes responsible for controlling extracellular adenosine levels in zebrafish brain. These findings could be relevant to evaluate potential beneficial effects promoted by acute taurine treatment in the central nervous system (CNS) of this species.
Rosemberg
Denis Broock
DB
Programa de Pós-graduação em Bioquímica, Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul., Rua Ramiro Barcelos 2600-Anexo, 90035-003 Porto Alegre, RS, Brazil. dbrosemberg@gmail.com
Kist
Luiza Wilges
LW
Etchart
Renata Jardim
RJ
Rico
Eduardo Pacheco
EP
Langoni
Andrei Silveira
AS
Dias
Renato Dutra
RD
Bogo
Maurício Reis
MR
Bonan
Carla Denise
CD
Souza
Diogo Onofre
DO
D015720:5'-Nucleotidase / Q000378:metabolism; D000243:Adenosine Deaminase / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000249:Adenosine Monophosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000648:ultrastructure*; D002462:Cell Membrane / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D057075:Enzyme Assays; D045604:Extracellular Fluid / Q000187:drug effects* / Q000201:enzymology; D006868:Hydrolysis / Q000187:drug effects; D013654:Taurine / Q000494:pharmacology*; D015027:Zebrafish
D013654:Taurine; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D015720:5'-Nucleotidase; D000243:Adenosine Deaminase