In vivo effects of high phenylalanine blood levels on Na+,K+-ATPase, Mg2+-ATPase activities and biogenic amine concentrations in phenylketonuria.
OBJECTIVE
To evaluate the activities of Na+,K+-ATPase and Mg2+-ATPase in erythrocyte membranes from phenylketonuric (PKU) patients and to correlate the enzyme activities with their blood phenylalanine (Phe) levels, biogenic amines as well as with their precursors tyrosine (Tyr) and tryptophan (Try).


METHODS
Twenty three PKU patients were divided into group A (n = 12) on a restricted diet (Phe 1.57 +/- 0.52 mg/dL or 0.10 +/- 0.03 mM) and group B (n = 11) on a "loose" diet (Phe 24.45 +/- 1.50 mg/dL or 1.72 +/- 0.09 mM). The enzyme activities were measured spectrophotometrically, the amino acids with an automatic amino analyser and the biogenic amines with HPLC methods.


RESULTS
In group B, plasma amino acids (Tyr, Try), their biogenic amines [adrenaline (A), noradrenaline (NA), dopamine (DA) and serotonin (5HT)], (Na+,K+)-ATPase and Mg2+-ATPase activities were found remarkably decreased (p < 0.001).


CONCLUSIONS
High Phe and/or low NA, DA, 5HT plasma levels may indirectly inhibit the erythrocyte membrane Na+,K+-ATPase and Mg2+-ATPase in PKU patients. The observed enzyme inhibitions could be a very informative peripheral marker as regards the neurotoxic Phe brain effects.
Institute of Child Health, "Aghia Sophia" Children's Hospital, Athens, Greece.
Kleopatra H
KH
Schulpis
Joanna
J
Tjamouranis
George A
GA
Karikas
Helen
H
Michelakakis
Stylianos
S
Tsakiris
D024322:Amino Acids, Aromatic / Q000097:blood; D000704:Analysis of Variance; D001679:Biogenic Amines / Q000097:blood*; D017301:Ca(2+) Mg(2+)-ATPase / Q000097:blood*; D002648:Child; D004910:Erythrocyte Membrane / Q000201:enzymology*; D006801:Humans; D010649:Phenylalanine / Q000097:blood*; D010661:Phenylketonurias / Q000097:blood* / Q000178:diet therapy / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000097:blood*; D013223:Statistics as Topic
D024322:Amino Acids, Aromatic; D001679:Biogenic Amines; D010649:Phenylalanine; D017301:Ca(2+) Mg(2+)-ATPase; D000254:Sodium-Potassium-Exchanging ATPase