title: Hyperphenylalaninemia reduces creatine kinase activity in the cerebral cortex of rats.
abstract: Phenylketonuria (PKU) is a metabolic disorder accumulating phenylalanine (Phe) and its metabolites in plasma and tissues of the patients. Considering that phenylalanine is the main neurotoxic metabolite, and brain energy homeostasis seems to be affected in phenylketonuria, our main objective was to investigate the effect of acute and chronic hyperphenylalaninemia (HPA) on creatine kinase (CK) activity in brain cortex of Wistar rats. Hyperphenylalaninemia was induced by subcutaneous administration of 5.2 micromol phenylalanine + 2.4 micromol alpha-methylphenylalanine (phenylalanine hydroxylase (PAH) inhibitor)/g of body weight. We also investigated the in vitro effect of phenylalanine and/or alpha-methylphenylalanine on creatine kinase activity in the brain cortex of non-treated rats. The results showed that phenylalanine significantly inhibited creatine kinase activity in vitro and reduced the enzyme activity in vivo. Considering the importance of creatine kinase for the maintenance of energy homeostasis in brain, if this enzyme inhibition also occurs in phenylketonuric patients, it is possible that creatine kinase inhibition may be one of the mechanisms by which phenylalanine is neurotoxic in phenylketonuria.
authors.affiliation: Departamento de Bioqui;mica, Instituto de Ciências Básicas da Saúde, UFRGS, Rua Ramiro Barcelos 2600, CEP 90.035-003, RS, Porto Alegre, Brazil.
authors.forename: Elisa
authors.initials: E
authors.lastname: Costabeber
authors.forename: Adriana
authors.initials: A
authors.lastname: Kessler
authors.forename: Carlos
authors.initials: C
authors.lastname: Severo Dutra-Filho
authors.forename: Angela Terezinha
authors.initials: AT
authors.lastname: de Souza Wyse
authors.forename: Moacir
authors.initials: M
authors.lastname: Wajner
authors.forename: Clóvis Milton Duval
authors.initials: CM
authors.lastname: Wannmacher
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000201:enzymology*; D003402:Creatine Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D010661:Phenylketonurias / Q000139:chemically induced / Q000201:enzymology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D004791:Enzyme Inhibitors; C012436:alpha-methylphenylalanine; D010649:Phenylalanine; D003402:Creatine Kinase