Tyrosine supplementation in phenylketonuria: Diurnal blood tyrosine levels and presumptive brain influx of tyrosine and other large neutral amino acids

摘要: Abstract Tyrosine supplementation has not consistently been found to improve neuropsychologic function in phenylketonuria (PKU), possibly because of failure achieve adequate levels tyrosine the brain. Objectives: To evaluate blood achieved after treated PKU and calculate brain influxes other large neutral amino acids before with supplementation. Study design: Ten subjects receiving a phenylalanine-restricted diet were studied over 48 hours; each received (300 mg/kg) on day 2. Plasma phenylalanine measured every 2 hours, all free 6 hours. Brain calculated. Results: low normal at baseline. With there was substantial but unsustained rise plasma tyrosine. Calculated influx 27% ± 19% supplementation, increasing 90% 58% Nevertheless, calculated remained less than 70% 50% time points. The except tryptophan 20% 40% Conclusions: for produces marked nonsustained increases levels, that often remains suboptimal. This could explain lack consistent benefit (J Pediatr 2001;139:421-7)