ATTACHMENT OF RADIOMETALS TO LDL WITH LIPID ANALOGS OF EDTA OR DTPA TYPE COMPLEXING AGENTS - COMPARISON OF 2 LABELING PROCEDURES

Two methods are compared for labeling LDL with a radiometal (M = In-11 1, Gd-153) through a lipid anchor (L). Three EDTA or DTPA type complex ing agents derived from stearylamine or phosphatidylethanolamine were used. In procedure A, the L-LDL conjugate is first prepared and then l abeled with M. in procedure B, the complex M-L is first prepared and t hen inserted into the LDL. In both procedures the final particle is M- L-LDL. After precipitation of free radiometals (adding tropolone) or o f the M-L-LDL particles (adding heparine), radioactivity counting show s that 55 to 92% or 55 to 85% of the initial amount of M remains attac hed to the M-L-LDL particles in procedures A and B, respectively. Thes e two procedures may be used for labeling LDL with a radiometal.