What mechanism of localization does Tc succimer (DMSA) use?

• A. Passive diffusion
• B. Active transport
• C. Filtration
• D. Protein binding

Answer: (B)

Tc succimer (DMSA) localizes in tissues primarily through active transport mechanisms. This involves the selective uptake of the radiopharmaceutical by cells via specific transport proteins or receptor-mediated endocytosis. In this case, succimer acts as a chelating agent that binds to technetium and is recognized by particular cellular uptake systems, leading to a concentrated accumulation in certain organs, particularly the kidneys, which are known to have a high affinity for this compound.

Active transport is crucial because it allows for the concentration of Tc-DMSA in the targeted tissues against a concentration gradient, which passive diffusion would not achieve. This characteristic enhances the effectiveness of Tc succimer as a radiopharmaceutical, as it can provide clearer images and better diagnostic capability for imaging studies. Thus, the mechanism of active transport is fundamental to how Tc succimer functions in medical imaging applications.