Abstract
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 < 0.005). Conclusion: 125I-IMT transport was hLAT1 selective. Investigations on the isoform selectivity of 125I-IMT transport with other transporters are anticipated.
- membrane transport
- 3-125I-iodo-α-methyl-l-tyrosine
- human L-type amino acid transporter family
- human 4F2hc
- Xenopus laevis oocyte
Footnotes
Received Apr. 10, 2002; revision accepted Sep. 25, 2002.
For correspondence or reprints contact: Naoto Shikano, MS, Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Ami-machi, Inashiki-gun, Ibaraki 300-0394, Japan.
E-mail: sikano{at}ipu.ac.jp