Understanding the in vivo Uptake Kinetics of a Phosphatidylethanolamine-binding Agent 99mTc-Duramycin
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Nuclear Medicine and Biology
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99mTc-Duramycin is a peptide-based molecular probe that binds specifically to phosphatidylethanolamine (PE). The goal was to characterize the kinetics of molecular interactions between 99mTc-Duramycin and the target tissue.
High level of accessible PE is induced in cardiac tissues by myocardial ischemia (30 min) and reperfusion (120 min) in Sprague–Dawley rats. Target binding and biodistribution of 99mTc-duramycin were captured using SPECT/CT. To quantify the binding kinetics, the presence of radioactivity in ischemic versus normal cardiac tissues was measured by gamma counting at 3, 10, 20, 60 and 180 min after injection. A partially inactivated form of 99mTc-Duramycin was analyzed in the same fashion. A compartment model was developed to quantify the uptake kinetics of 99mTc-Duramycin in normal and ischemic myocardial tissue.
99mTc-duramycin binds avidly to the damaged tissue with a high target-to-background radio. Compartment modeling shows that accessibility of binding sites in myocardial tissue to 99mTc-Duramycin is not a limiting factor and the rate constant of target binding in the target tissue is at 2.2 ml/nmol/min/g. The number of available binding sites for 99mTc-Duramycin in ischemic myocardium was estimated at 0.14 nmol/g. Covalent modification of D15 resulted in a 9-fold reduction in binding affinity.
99mTc-Duramycin accumulates avidly in target tissues in a PE-dependent fashion. Model results reflect an efficient uptake mechanism, consistent with the low molecular weight of the radiopharmaceutical and the relatively high density of available binding sites. These data help better define the imaging utilities of 99mTc-Duramycin as a novel PE-binding agent.
Audi, Said H.; Li, Zhixin; Capacete, Joseph; Liu, Yu; Fang, Wei; Shu, Laura G.; and Zhao, Ming, "Understanding the in vivo Uptake Kinetics of a Phosphatidylethanolamine-binding Agent 99mTc-Duramycin" (2012). Biomedical Engineering Faculty Research and Publications. 251.
Accepted version. Nuclear Medicine and Biology, Vol. 39, No. 6 (August 2012): 821-825. DOI. © 2012 Elsevier. Used with permission.
NOTICE: this is the author’s version of a work that was accepted for publication in Nuclear Medicine and Biology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Nuclear Medicine and Biology, VOL 39, ISSUE 6, August 2012, DOI.