Evaluation of potential tracer ability of (99m)Tc-labeled acetylated LDL for scintigraphy of LDL-scavenger receptor sites of macrophageal origin.

Low-density lipoprotein (LDL) receptors are ubiquitously present in a variety of human tissues. Scavenger receptors, which are the activated macrophages bearing receptors for modified LDL, have been shown to be densely located at the atherosclerotic lesions. Acetylated LDL competes with oxidized LDL for access to these receptors. The present study was undertaken to optimize (99m)Tc labeling of two different forms of LDLs [i.e., native (Na) and acetylated (Ac)] and to explore their utility for the scintigraphy of densely localized scavenger LDL-receptor activity in vivo. Native and acetyl-LDL were labeled with (99m)Tc using sodium dithionite as a reducing agent. Significant hepatic and muscular uptake precluded optimal availability of (99m)Tc-Ac-LDL in blood, which favors macrophageal binding in sterile abscess models in rabbits. (99m)Tc-Ac-LDL behave as a novel tracer for imaging densely localized scavenger receptor sites constituted by activated macrophages at the site of independent inflammatory lesions and appears promising for the scintigraphy of atherosclerotic lesions.