PT - JOURNAL ARTICLE AU - Naoto Shikano AU - Yoshikatsu Kanai AU - Keiichi Kawai AU - Jun Inatomi AU - Do Kyung Kim AU - Nobuyoshi Ishikawa AU - Hitoshi Endou TI - Isoform Selectivity of 3-<sup>125</sup>I-Iodo-α-Methyl-<span class="sc">l</span>-Tyrosine Membrane Transport in Human L-Type Amino Acid Transporters DP - 2003 Feb 01 TA - Journal of Nuclear Medicine PG - 244--246 VI - 44 IP - 2 4099 - http://jnm.snmjournals.org/content/44/2/244.short 4100 - http://jnm.snmjournals.org/content/44/2/244.full SO - J Nucl Med2003 Feb 01; 44 AB - 3-123I-Iodo-α-methyl-l-tyrosine (123I-IMT) has been developed for SPECT of amino acid transport imaging. We examined the isoform selectivity of 125I-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 125I-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 125I-IMT was measured in the Na+-free uptake solution containing 18.5 kBq of noncarrier-added 125I-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, 125I-IMT uptake via hLAT1 was 5.95-fold higher than that via hLAT2 (P &lt; 0.005). Conclusion: 125I-IMT transport was hLAT1 selective. Investigations on the isoform selectivity of 125I-IMT transport with other transporters are anticipated.