Impaired phenylalanine-tyrosine conversion in patients with iron-deficiency anemia studied by a L-(2H5)phenylalanine-loading test.
Ten patients with manifest iron deficiency and without documented relationship to phenylketonuria patients were orally loaded with 25 mg/kg of L-(2H5)phenylalanine. Before loading, the fasting phenylalanine-tyrosine plasma ratio was determined and after loading, the concentrations of labeled and nonlabeled phenylalanine and tyrosine were determined in five consecutive plasma samples. With respect to the fasting phenylalanine-tyrosine ratio and to the post-load ratios of labeled phenylalanine over labeled tyrosine, the iron-deficient patients showed data intermediate between those of normals and heterozygotes for phenylketonuria. Compared to a 100% in vivo activity of phenylalanine hydroxylase in normals and a circa 37% activity in heterozygotes for classic phenylketonuria, iron-deficient patients with an average hemoglobin of 8.6 +/- 1 g/dl showed an activity of circa 56%. After normalization of their iron status, four patients were subjected again to the L-(2H5)phenylalanine-loading test. For three of these individuals, test results shifted into the range of normal.
D000328:Adult; D000747:Anemia, Hypochromic / Q000097:blood* / Q000188:drug therapy; D005215:Fasting; D005260:Female; D006580:Genetic Carrier Screening; D006801:Humans; D007501:Iron / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010649:Phenylalanine / Q000097:blood; D010651:Phenylalanine Hydroxylase / Q000378:metabolism; D010661:Phenylketonurias / Q000235:genetics; D014443:Tyrosine / Q000097:blood*
D014443:Tyrosine; D010649:Phenylalanine; D007501:Iron; D010651:Phenylalanine Hydroxylase