Technetium-99m low density lipoproteins: Preparation and biodistribution

The focal uptake by human atherosclerotic lesions of ¹²⁵I bound to low density lipoproteins (LDL) can be demonstrated by external imaging. However, ¹²⁵I has poor imaging characteristics. Therefore, we have developed a technique for labeling LDL with technetium. To facilitate analysis, LDL was first labeled with ^99mTc, by reduction of TcO₄^- with dithionite in the presence of the protein. The labeled LDL was stable to electrophoresis, ultracentrifugation, and passage in vivo. This technique was repeated with minor modification with ^99mTc to prepare [^99mTc] LDL for use as an imaging agent. Its biodistribution in 16 rabbits was similar to that of [¹²⁵I]LDL and it allowed high resolution external imaging of LDL uptake by tissues, including the injured, healing, arterial wall, and the adrenal cortex.