Isoform selectivity of 3-125I-iodo-alpha-methyl-L-tyrosine membrane transport in human L-type amino acid transporters.
3-(123)I-Iodo-alpha-methyl-L-tyrosine ((123)I-IMT) has been developed for SPECT of amino acid transport imaging. We examined the isoform selectivity of (125)I-IMT transport of the 2 human L-type amino acid transporters, hLAT1 and hLAT2, with human 4F2hc-coexpressed Xenopus laevis oocytes.


METHODS
An uptake study of (125)I-IMT was performed using transporter-expressed X. laevis oocytes. Oocytes were injected with 17.6 ng of hLAT1 or hLAT2 complementary RNA (cRNA) and 7.4 ng of h4F2hc cRNA in a molar ratio of 1:1. Two days after injection, the uptake of (125)I-IMT was measured in the Na(+)-free uptake solution containing 18.5 kBq of noncarrier-added (125)I-IMT. After incubation for 30 min at room temperature, radioactivity of the oocytes was determined.


RESULTS
Of the 2 hLAT isoforms and h4F2hc-coexpressed X. laevis oocytes, (125)I-IMT uptake via hLAT1 was 5.95-fold higher than that via hLAT2 (P < 0.005).


CONCLUSIONS
(125)I-IMT transport was hLAT1 selective. Investigations on the isoform selectivity of (125)I-IMT transport with other transporters are anticipated.
Shikano
Naoto
N
Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, Ibaraki, Japan. sikano@ipu.ac.jp
Kanai
Yoshikatsu
Y
Kawai
Keiichi
K
Inatomi
Jun
J
Kim
Do Kyung
DK
Ishikawa
Nobuyoshi
N
Endou
Hitoshi
H
D027182:Amino Acid Transport System y+; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D027301:Fusion Regulatory Protein 1, Light Chains / Q000378:metabolism*; D006801:Humans; D027283:Large Neutral Amino Acid-Transporter 1 / Q000378:metabolism*; D008781:Methyltyrosines / Q000493:pharmacokinetics*; D009865:Oocytes / Q000000981:diagnostic imaging / Q000378:metabolism*; D010865:Pilot Projects; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013237:Stereoisomerism; D014982:Xenopus laevis
D027182:Amino Acid Transport System y+; D027301:Fusion Regulatory Protein 1, Light Chains; D027283:Large Neutral Amino Acid-Transporter 1; D008781:Methyltyrosines; D019275:Radiopharmaceuticals; C420646:SLC7A8 protein, human; C030855:3-iodo-alpha-methyltyrosine