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Intracellular phenylalanine and tyrosine concentration in homozygotes and heterozygotes for phenylketonuria (PKU) and hyperphenylalaninemia compared with normals. 1982

O Thalhammer, and G Lubec, and H Königshofer, and S Scheibenreiter, and H Coradello

Assuming adequate technique, determinations of intracellular phenylalanine and tyrosine concentrations in lymphocytes are very reproducible. The concentrations found in this study (1981) in five homozygotes and five obligate heterozygotes for PKU and seven normals, are identical with the corresponding concentrations found in 1979 in 13 homo- and 19 obligate heterozygotes for PKU and 26 normals. The intracellular concentrations in six homo- and five heterozygotes for hyper-Phe, as determined in the present study, are intermediate between the concentrations found in PKUs and normals in the present and the former study. As in PKUs, there is no difference between homo- and heterozygotes for hyper-Phe. The hypothesis of an intracellular threshold concentration for phenylalanine triggering the production of a toxic metabolite, could explain the severe brain damage observed in untreated PKU-homozygotes, the slight damage in well-treated PKU-homozygotes and in PKU-heterozygotes, and the absence of damage in hyper-Phe homozygotes (and heterozygotes). Also the difference in brain function between homozygotes for both conditions (PKU-treated), can be understood in spite of comparably elevated extracellular phenylalanine concentrations in young patients.

UI MeSH Term Description Entries
D007231 Infant, Newborn An infant during the first 28 days after birth. Neonate,Newborns,Infants, Newborn,Neonates,Newborn,Newborn Infant,Newborn Infants
D008214 Lymphocytes White blood cells formed in the body's lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each), or NATURAL KILLER CELLS. Lymphoid Cells,Cell, Lymphoid,Cells, Lymphoid,Lymphocyte,Lymphoid Cell
D008297 Male Males
D010649 Phenylalanine An essential aromatic amino acid that is a precursor of MELANIN; DOPAMINE; noradrenalin (NOREPINEPHRINE), and THYROXINE. Endorphenyl,L-Phenylalanine,Phenylalanine, L-Isomer,L-Isomer Phenylalanine,Phenylalanine, L Isomer
D010661 Phenylketonurias A group of autosomal recessive disorders marked by a deficiency of the hepatic enzyme PHENYLALANINE HYDROXYLASE or less frequently by reduced activity of DIHYDROPTERIDINE REDUCTASE (i.e., atypical phenylketonuria). Classical phenylketonuria is caused by a severe deficiency of phenylalanine hydroxylase and presents in infancy with developmental delay; SEIZURES; skin HYPOPIGMENTATION; ECZEMA; and demyelination in the central nervous system. (From Adams et al., Principles of Neurology, 6th ed, p952). Biopterin Deficiency,Dihydropteridine Reductase Deficiency Disease,Hyperphenylalaninemia, Non-Phenylketonuric,Phenylalanine Hydroxylase Deficiency Disease,BH4 Deficiency,DHPR Deficiency,Deficiency Disease, Dihydropteridine Reductase,Deficiency Disease, Phenylalanine Hydroxylase,Deficiency Disease, Phenylalanine Hydroxylase, Severe,Dihydropteridine Reductase Deficiency,Folling Disease,Folling's Disease,HPABH4C,Hyperphenylalaninaemia,Hyperphenylalaninemia Caused by a Defect in Biopterin Metabolism,Hyperphenylalaninemia, BH4-Deficient, C,Hyperphenylalaninemia, Tetrahydrobiopterin-Deficient, Due To DHPR Deficiency,Non-Phenylketonuric Hyperphenylalaninemia,Oligophrenia Phenylpyruvica,PAH Deficiency,PKU, Atypical,Phenylalanine Hydroxylase Deficiency,Phenylalanine Hydroxylase Deficiency Disease, Severe,Phenylketonuria,Phenylketonuria I,Phenylketonuria II,Phenylketonuria Type 2,Phenylketonuria, Atypical,Phenylketonuria, Classical,QDPR Deficiency,Quinoid Dihydropteridine Reductase Deficiency,Tetrahydrobiopterin Deficiency,Atypical PKU,Atypical Phenylketonuria,Biopterin Deficiencies,Classical Phenylketonuria,Deficiency, BH4,Deficiency, Biopterin,Deficiency, DHPR,Deficiency, Dihydropteridine Reductase,Deficiency, PAH,Deficiency, Phenylalanine Hydroxylase,Deficiency, QDPR,Deficiency, Tetrahydrobiopterin,Disease, Folling,Disease, Folling's,Hyperphenylalaninemia, Non Phenylketonuric,Non Phenylketonuric Hyperphenylalaninemia,Non-Phenylketonuric Hyperphenylalaninemias
D005260 Female Females
D006579 Heterozygote An individual having different alleles at one or more loci regarding a specific character. Carriers, Genetic,Genetic Carriers,Carrier, Genetic,Genetic Carrier,Heterozygotes
D006720 Homozygote An individual in which both alleles at a given locus are identical. Homozygotes
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328 Adult A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available. Adults

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