, Volume 11, Issue 3, pp 285-290

Serotonin and noradrenaline concentrations and serotonin uptake in platelets from hyperphenylalaninaemic patients

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In three untreated patients with phenylketonuria (PKU), three PKU and six hyperphenylalaninaemic (HPA) patients in good metabolic control, the kinetic constants of plateletin vitro uptake of [14C]serotonin (5HT) did not significantly differ from those in 12 control subjects matched for age. The platelet concentrations of endogenous 5HT and noradrenaline (NA), taken as long-term indices of the amount of these amines circulating in plasma, were lower than normal in PKU and HPA patients, whether or not they were kept on a diet. However, a reduction in plasma NA concentrations at the moment of blood collection was seen only in untreated PKU patients. These data indicate that there may be a chronic inhibition of 5HT and possibly of NA synthesis even in PKU or HPA subjects in good metabolic control, with normal psychomotor development and only slightly raised plasma phenylalanine levels.