Kinetic parameters of 3-[(123)I]iodo-L-alpha-methyl tyrosine ([(123)I]IMT) transport in human GOS3 glioma cells.

The radiolabelled amino acid 3-[(123)I]iodo-L-alpha-methyl tyrosine ([(123)I]IMT) is a promising tool for the diagnosis and monitoring of brain tumors using single-photon emission tomography (SPECT). However, little is known about the precise kinetics of [(123)I]IMT uptake in human glioma cells. The kinetic analysis of [(123)I]IMT transport in human GOS3 glioma cells yielded a high-affinity apparent Michaelis constant (K(m) = 20.1 +/- 1.5 microM). The maximum transport velocity (V(max)) amounted to 34.8 +/- 1.9 nmol/mg protein/10 min. Competitive inhibition experiments revealed that [(123)I]IMT transport is mediated principally by the sodium-independent system L.