Premium
Characterization of 3‐[ 123 I]iodo‐ L ‐α‐methyl tyrosine transport in astrocytes of neonatal rats
Author(s) -
Kopka Klaus,
Riemann Burkhard,
Friedrich Matthias,
Winters Silke,
Halfter Hartmut,
Weckesser Matthias,
Stögbauer Florian,
Ringelstein E. Bernd,
Schober Otmar
Publication year - 2001
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2001.00048.x
Subject(s) - glioma , astrocyte , sodium , chemistry , biology , endocrinology , cancer research , central nervous system , organic chemistry
3‐[ 123 I]Iodo‐ L ‐α‐methyl tyrosine ( 123 I‐IMT) is used for diagnosis and monitoring of brain tumours by means of single‐photon emission tomography. As recently shown, 123 I‐IMT is predominantly mediated into rat C6 glioma cells by sodium‐independent system L for large neutral amino acids. Until now, 123 I‐IMT transport in non‐neoplastic glial cells has not been examined. Therefore, the aim of this study was to examine the cellular pathways and precise transport kinetics of 123 I‐IMT uptake into astrocytes of neonatal rats. In particular sodium‐independent 123 I‐IMT transport into neonatal astrocytes was compared with sodium‐independent 123 I‐IMT uptake into neoplastic rat C6 glioma cells. Competitive inhibition experiments showed that 123 I‐IMT is exclusively transported via sodium‐independent system L into the neonatal astrocytes (92%). Kinetic analysis of sodium‐independent 123 I‐IMT uptake into neonatal astrocytes and into C6 glioma cells revealed apparent Michaelis constants K M = 13.9 ± 0.5 µ m and K M = 33.9 ± 4.1 µ m , respectively, which are in the same range of K M values as those recently determined for amino acid transport into neoplastic and non‐neoplastic glial cells. Indeed, the K M values in the micromolar range correspond to the expression of the LAT‐1 subunit of system L both in the neonatal astrocytes and in C6 glioma cells. However, sodium‐independent maximum transport velocities ( V max ) differed significantly between neonatal astrocytes and C6 glioma cells (11.1 ± 0.3 and 39.9 ± 3.3 nmol/mg protein/10 min, respectively).