Experimental Study of 99mTc-Metallothionein Biodistribution in Intact Animals

Metallothioneins are a special group of low-molecular-weight proteins with metal-binding properties, which make them promising chelators for the development of targeted radiopharmaceuticals, as well as with technetium-99m. The aim of this work is to study the biodistribution of ^99mTc-metallothionein conjugate (^99mTc-MT) in intact mice in comparison with unbound technetium-99m (Na^99mTcO₄). Low uptake of ^99mTc-MT in the thyroid gland (1.20 ± 0.30%/g versus 267.2 ± 59.0%/g for Na^99mTcO₄) demonstrates the high stability of ^99mTc-MT in vivo. The ^99mTc-MT complex is rapidly eliminated from the bloodstream through the kidneys and is characterized by a reduced uptake in most organs and tissues compared to Na^99mTcO₄.