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Imaging Tc-99m-labeled FGF-1 targeting in rats
K R Zinn1, S Kelpke, T R Chaudhuri
1Division of Nuclear Medicine, Department of Radiology, University of Alabama, Birmingham, USA. kurtzinn@uab.edu
Nuclear Medicine and Biology
|August 12, 2000
Summary
This study developed a new method to radiolabel human acidic fibroblast growth factor (FGF-1) for imaging. The labeled FGF-1 maintained its biological activity and showed specific binding in rats, demonstrating potential for targeted imaging applications.
Area of Science:
- Biochemistry
- Radiochemistry
- Molecular Biology
Background:
- Recombinant human acidic fibroblast growth factor (FGF-1) plays crucial roles in cell growth and tissue repair.
- Developing effective methods for imaging FGF-1 distribution and targeting is essential for understanding its biological functions and therapeutic potential.
- Radiolabeling techniques are vital for non-invasive molecular imaging of biological molecules.
Purpose of the Study:
- To develop and validate a novel method for radiolabeling recombinant human acidic fibroblast growth factor (FGF-1) using technetium-99m (99mTc).
- To assess the biological activity, binding characteristics, and in vivo biodistribution of the radiolabeled FGF-1.
- To investigate the influence of heparin on the biodistribution of 99mTc-FGF-1.
Main Methods:
- Recombinant human acidic fibroblast growth factor (FGF-1) was radiolabeled with 99mTc using the hydrazinonicotinamide (HYNIC) conjugation method.
- The radiolabeled 99mTc-FGF-1 was characterized for molecular mass, heparin affinity, and cellular binding to low and high affinity sites.
- In vivo studies involved intravenous administration of 99mTc-FGF-1 in rats, followed by gamma camera imaging to determine biodistribution, with and without heparin co-administration.
Main Results:
- The radiolabeling process successfully produced 99mTc-FGF-1 that retained its molecular mass, heparin affinity, and mitogenic activity.
- Cellular binding assays confirmed the presence of both low (Kd = 9.5 nM) and high (Kd = 125 pM) affinity binding sites for 99mTc-FGF-1.
- In vivo imaging revealed significant uptake of 99mTc-FGF-1 in the liver and kidneys of rats.
- Co-administration of heparin significantly reduced liver uptake and increased urinary excretion of 99mTc-FGF-1.
Conclusions:
- The HYNIC method provides a reliable approach for radiolabeling FGF-1 with 99mTc, preserving its biological integrity and function.
- The biodistribution studies demonstrate the potential of 99mTc-FGF-1 for imaging FGF-1 targeting in vivo.
- Heparin influences the biodistribution of 99mTc-FGF-1, suggesting a role in modulating its clearance and tissue localization.