URINARY PHENYLKETO ACIDS IN PHENYLKETONURIA. OBSERVATION BY MEANS OF GAS CHROMATOGRAPHY AND GAS-MASS SPECTROMETRY.
It is necessary to estimate urinary excretion of phenylheto acids (PKA's) for the differential diagnosis of classical phenylketonuria (PKU) from common phenylalaninemia of various origins as well as for the observation of therapeutic effect of diets on PKU. Urine specimens were collected from six patients of PKU and eight heterozygotes of PKU belonging to 3 independent families. PKA's were extracted from urine specimens into ethylacetate and silylated so that it might be subjected to gas chromatographic (adsorbent OV-1) and gas-mass spectrometric studies. PKA's produced by the abnormal metabolic pathway of phenylalanine (Phe) in PKU were identified gas chromatographically with phenylacetic acid, mandelic acid, o-hydroxyphenylacetic acid, phenyllactic acid and phenylpyruvic acid. Their elution peaks appeared in the order listed above, with millimolar ratio of 1:1: 3.1: 25.7: 46.5 in the untreated and stationary PKU patients. This ratio remained in a satisfactorily narrow range to the extent that its calculation is thought to be helpful for differential diagnosis of PKU from hyperphenylalaninemias of etiologically varived types. No significant peaks of these five PKA's were seen gaschromatographically with the urines of PKU heterozygotes as well as with those of the normal subjects. However, one point worthy of special mentioning is a transitory appearance of extremely flattened (or equivocal) PKA peaks with the urines collected from the PKU heterozygotes for 6 hours after Phe-loading. This is suggestive of a compensatory reaction of heterozygotes in response to administration of large amount of Phe. In the authors experience gas chromatography provided the most sensitive and reliable measure of the various diagnostic tests for PKU, and mass spectrometer proved to be a powerful tool for identification of PKA's.
