title: Plasma biopterin levels and tetrahydrobiopterin responsiveness.
abstract: Tetrahydrobiopterin (BH4) responsive hyperphenylalaninemia (HPA) with a mutant phenylalanine hydroxylase (PAH) gene was found during neonatal screening for PKU. This study determined blood BH4 and phenylalanine in two patients with hyperphenylalaninemia following oral load with BH4 10 mg/kg. Our patients underwent neonatal screening for PKU, had normal biopterin metabolism and their PAH mutations were determined. Peak plasma biopterin levels in Case 1, which were reached at between 2 and 4h after loading, were 612, 297, and 178 nmol/L at age 30 days, 55 days, and 19 months, respectively, and the maximum phenylalanine decreasing rates, which were found at 24h, were 54, 16, and 4%, respectively. In Case 2, peak plasma biopterin levels were 747 and 327 nmol/L at age 20 and 55 days, respectively, and the maximum phenylalanine decreasing rates were 39 and 32%, respectively. In the BH4 loading test, the peaks of BH4 in both patients lowered ( approximately 50%), on the same dose schedule of BH4, as patients got older.
authors.affiliation: Department of Pediatrics, Osaka City University Graduate School of Medicine, Osaka 545-8585, Japan. shintakuh@med.osaka-cu.ac.jp
authors.forename: Haruo
authors.initials: H
authors.lastname: Shintaku
authors.forename: Hiroki
authors.initials: H
authors.lastname: Fujioka
authors.forename: Yoshitomo
authors.initials: Y
authors.lastname: Sawada
authors.forename: Minoru
authors.initials: M
authors.lastname: Asada
authors.forename: Tsunekazu
authors.initials: T
authors.lastname: Yamano
mesh_terms: D001708:Biopterins / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D010649:Phenylalanine / Q000097:blood*; D010651:Phenylalanine Hydroxylase / Q000235:genetics; D010661:Phenylketonurias / Q000097:blood* / Q000235:genetics
chemical_list: D001708:Biopterins; D010649:Phenylalanine; D010651:Phenylalanine Hydroxylase; C003402:sapropterin