Guanine and adenine nucleotidase activities in rat cerebrospinal fluid

• Published in: Brain research 2002-09, Vol.950 (1), p.74-78
• Main Authors: Portela, Luis Valmor Cruz, Oses, Jean Pierre, Silveira, André Luiz, Schmidt, André Prato, Lara, Diogo Rizzato, Battastini, Ana Maria Oliveira, Ramirez, Galo, Vinadé, Lúcia, Sarkis, João José Freitas, Souza, Diogo Onofre
• Format: Article
• Language: English
• Subjects: Adenine Nucleotides - cerebrospinal fluid; Adenine Nucleotides - metabolism; Adenosine; ADPase and GDPase; Animals; Biological and medical sciences; Cerebral circulation. Blood-brain barrier. Choroid plexus. Cerebrospinal fluid. Circumventricular organ. Meninges; Female; Fundamental and applied biological sciences. Psychology; Guanine Nucleotides - cerebrospinal fluid; Guanine Nucleotides - metabolism; Guanosine; Hydrolysis; Nucleotidase; Nucleotidases - cerebrospinal fluid; Nucleotidases - metabolism; Rat CSF; Rats; Rats, Wistar; Vertebrates: nervous system and sense organs
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(02)02987-6

Adenine and guanine nucleotides have been shown to exert multiple roles in central and peripheral nervous systems, and the sequential breakdown of these nucleotides by enzymatic systems is an important step in the modulation of their extracellular effects. The aim of this study was to investigate whether nucleotide hydrolysis also occurs in the cerebrospinal fluid (CSF) of rats. CSF was able to hydrolyze all guanine and adenine nucleotides investigated (2.0 mM): GDP≫ADP=ATP=GTP≫AMP=GMP. More detailed studies with the diphosphate nucleotides showed that the hydrolysis of ADP and GDP was linear with incubation time and protein concentration. The apparent K M (Henry–Michaelis–Menten constant) and V (maximal velocity) values for ADP and GDP were 164.3±54.7 μM and 12.2±3.8 nmol P i/min per mg protein, and 841.0±90.2 μM and 22.8±8.0 nmol P i/min per mg protein. The sum of ADP, GDP and UDP hydrolysis (2.0 mM) upon individual incubations with CSF was similar to the hydrolysis observed when all three nucleotides were incubated together. This pattern of hydrolysis strongly suggests the involvement of more than one enzyme activity. The higher maximum activity for GDP and UDP compared to ADP is compatible with presence of a soluble NTDPase5.