OtherBASIC SCIENCE INVESTIGATIONS

Competitive Displacement of Serum Protein Binding of Radiopharmaceuticals with Amino Acid Infusion Investigated with N-Isopropyl-p-123I-Iodoamphetamine

Noriyuki Kuga, Naoto Shikano, Norito Takamura, Ryuichi Nishii, Keishi Yamasaki, Masato Kobayashi, Shigeki Nagamachi, Shozo Tamura and Keiichi Kawai
Journal of Nuclear Medicine August 2009, 50 (8) 1378-1383; DOI: https://doi.org/10.2967/jnumed.108.060095

Article Figures & Data

Figures

  • FIGURE 1. 
    FIGURE 1. 

    Chemical structure of 123I-IMP.

  • FIGURE 2. 
    FIGURE 2. 

    Protein binding of 123I-IMP to serum, HSA, AGP, and IgG at concentrations of 740, 17, and 62 μM, respectively. Each column represents mean ± SD of 3 independent experiments.

  • FIGURE 3. 
    FIGURE 3. 

    Effects of binding site markers on 123I-IMP protein binding. Normal saline solution was used as control. Concentration of HSA in human serum was adjusted to 500 μM. Each site marker was loaded at 200 μM final concentration. Each column represents mean ± SD of 3 independent experiments. *P < 0.05.

  • FIGURE 4. 
    FIGURE 4. 

    Free fraction rates of radiolabeled chemicals (14C-warfarin [A], 14C-diazepam [B], and 3H-propranolol [C]) loaded with Proteamin (PTA) and Kidomin (KDM) in normal human serum. Concentration of HSA in human serum was adjusted to 700 μM, and 2.0-μL aliquots of amino acid infusion were added to 200.0 μL of radiolabeled chemical–human serum mixture. *P < 0.02 vs. control. **P < 0.003 vs. control.

  • FIGURE 5. 
    FIGURE 5. 

    123I-IMP whole-body scintigraphy (A) and brain SPECT (B) with or without Proteamin loading in same monkey (monkey 1). Proteamin (PTA; 5.0 mL) was loaded just before 123I-IMP injection. After 123I-IMP injection, Proteamin was also administered at 0.5 mL/min for 30 min.

  • FIGURE 6. 
    FIGURE 6. 

    Time–activity curves of 123I-IMP monkey 1 (A) and monkey 2 (B) on dynamic scintigraphy in same monkey. Findings with or without Proteamin (PTA) loading are shown for 123I-IMP accumulation in monkey.

Tables

  • TABLE 1

    Content of Amino Acid Infusions

    Amino acid infusion
    ContentProteaminKidomin
    L-arginine35.112.9
    L-histidine17.111.3
    L-isoleucine22.834.3
    L-leucine43.453.4
    L-lysine26.917.3
    L-methionine14.510.1
    L-phenylalanine29.515.1
    L-threonine21.214.7
    L-tryptophan4.66.1
    L-valine29.442.7
    Glycine104.4—
    L-proline46.213.0
    L-serine22.214.3
    L-aspartic acid7.63.8
    L-glutamic acid3.53.4
    L-tyrosine1.60.1
    L-cystine0.5—
    L-cysteine—4.1
    L-alanine46.114.0
    Total free amino acids476.6270.6

    • Data are mmol/L. Infusions also contain electrolytes and carbohydrates.

  • TABLE 2

    Free Fraction of 125I-IMP and Relative Free Fraction Rate with Proteamin and Kidomin

    Amino acid infusionFree fraction (%)Relative free fraction rate (fold)P*
    Control (saline)14.95 ± 0.74——
    Proteamin19.24 ± 0.871.29 ± 0.06<0.02
    Kidomin16.79 ± 0.871.12 ± 0.06<0.02

    • ↵* By paired t test. Control vs. amino acid infusion.

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