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J Nucl Med. 1991 Nov;32(11):2043-9.

The transport of tyrosine into the human brain as determined with L-[1-11C]tyrosine and PET.

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  • 1Department of Psychiatry, University of Uppsala, Sweden.

Abstract

An alteration of dopaminergic transmission in the brain has been proposed for schizophrenia. To explore this, the rate constant for the intransport of L-tyrosine across the blood-brain barrier in healthy controls and in patients with schizophrenia (DSM-III-R) was determined with PET and L-[1-11C] tyrosine as the tracer. Kinetics for tyrosine transport were determined according to a two-compartment model using radioactivity data of arterial blood and brain tissue sampled between 1 and 3.5 min after a bolus injection of L-[1-11C] tyrosine. Radioactivity was measured every second in the blood and in 10-sec intervals in the brain tissue. In the normal controls the brain intransport rate constant for tyrosine was 0.052 ml/g/min with an influx rate of 2.97 nmol/g/min. The patients had a similar intransport rate constant (0.045 ml/g/min) but a lower influx rate of tyrosine 1.95 nmol/g/min (p less than 0.05). The patients' tyrosine concentrations in the blood were lower. For data sampled between 5 and 25 min, the net accumulation rate of tyrosine into the brain was 0.015 ml/g/min in the controls which did not differ to the patients' rate. However, the net utilization of tyrosine was lower in the patients (0.672 nmol/g/min) than in the controls (0.883 nmol/g/min) despite similar tissue concentrations of tyrosine.

PMID:
1941137
[PubMed - indexed for MEDLINE]
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