Mercaptoacetyltriglycine

Mercaptoacetyltriglycine, commonly abbreviated MAG3, is a chelating ligand used to form the radiopharmaceutical technetium-99m mercaptoacetyltriglycine (Tc-99m MAG3). The molecule comprises a mercaptoacetyl group linked to a triglycine backbone, enabling effective coordination to technetium and resulting in a stable Tc-99m complex that is excreted primarily by the renal tubules.

Use in nuclear medicine centers on renal imaging. Tc-99m MAG3 is employed in renal dynamic scintigraphy to assess perfusion, function, and drainage of both kidneys. Following intravenous administration, serial gamma-camera images are acquired over 20 to 40 minutes, and time-activity curves for each kidney are analyzed to estimate parameters such as renal uptake, tubular excretion, and effective renal plasma flow. MAG3 provides information on tubular transport and overall renal function that complements measurements obtained with other agents.

Compared with some older radiopharmaceuticals, MAG3 tends to exhibit higher tubular extraction and faster clearance, making it well-suited for evaluating tubular function and drainage. Its imaging performance can be influenced by hepatic or biliary excretion in some cases, and radiation exposure considerations apply as with all nuclear medicine procedures.

Synthesis and chemistry: MAG3 is designed as a peptide-like chelating ligand that binds technetium in radiopharmaceutical preparations, typically forming a Tc(V)-oxo complex with the MAG3 ligand. The resulting complex is prepared for clinical use by radiolabeling with Tc-99m under standardized conditions.

See also: technetium-99m radiopharmaceuticals, renal scintigraphy, renography, tubular function assessment.