title: In vitro effect of homocysteine on nucleotide hydrolysis by blood serum from adult rats.
abstract: During the past few years, elevated blood levels of homocysteine (Hcy) have been linked to increased risk of premature coronary artery disease, stroke and thromboembolism. These processes can be also related to the ratio adenine nucleotide/adenosine, since extracellularly these nucleotides are associated with modulation of processes such as platelet aggregation, vasodilatation and coronary flow. Furthermore, there are some studies that suggest a relationship between Hcy and plasma adenosine concentrations. The sequential hydrolysis of ATP to adenosine by soluble nucleotidases constitutes one of the systems for rapid inactivation of circulating adenine nucleotides. Thus, the main objective of this study was to evaluate if Hcy can participate in the modulation of the extracellular adenine nucleotide hydrolysis by rat blood serum. Our results showed that Hcy, at final concentrations of 5.0 mM, inhibits in vitro ATP, ADP and AMP hydrolysis by 26, 21 and 16%, respectively. Also Hcy, at final concentrations of 8.0mM, inhibited the in vitro hydrolysis of ATP, ADP and AMP by 46, 44 and 44%, respectively. Kinetic analysis showed that the inhibitions of the three adenine nucleotide hydrolyses in the presence of Hcy, by serum of adult rats, is of the uncompetitive type. The IC50 calculated from the results obtained were 6.52+/-1.75 mM (n = 4), 5.18 +/- 0.64 mM (n = 3) and 5.16 +/- 1.22 mM (n = 3) for ATP, ADP and AMP hydrolysis, respectively.
authors.affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600-Anexo, CEP 90035-003, Porto Alegre, RS, Brazil.
authors.forename: Ana Elisa
authors.initials: AE
authors.lastname: Böhmer
authors.forename: Daniela
authors.initials: D
authors.lastname: Pochmann
authors.forename: João J F
authors.initials: JJ
authors.lastname: Sarkis
mesh_terms: D015720:5'-Nucleotidase / Q000378:metabolism; D000227:Adenine Nucleotides / Q000097:blood*; D000244:Adenosine Diphosphate / Q000097:blood; D000249:Adenosine Monophosphate / Q000097:blood; D000255:Adenosine Triphosphate / Q000097:blood; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006710:Homocysteine / Q000494:pharmacology*; D006868:Hydrolysis; D020128:Inhibitory Concentration 50; D008297:Male; D011755:Pyrophosphatases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000227:Adenine Nucleotides; D004791:Enzyme Inhibitors; D006710:Homocysteine; D000249:Adenosine Monophosphate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D015720:5'-Nucleotidase; D011755:Pyrophosphatases