Recent developments in receptor binding radiopharmaceuticals.

The stereoselective and saturable binding between receptor and ligand molecules plays an important role in many biological processes. Therefore ligand-receptor interactions have been increasingly studied in recent years by means of radionuclide labelled ligand molecules of high radiochemical purity and high specific activity. This contribution describes radiochemical development work of such radioligands performed at the Austrian Research Centre Seibersdorf in recent years: Tc99m-Neo-Galacto-Albumin was prepared as ligand for the Hepatic Binding Protein receptor, I-123-Low Density Lipoprotein (LDL) for LDL-receptors in the liver. Since LDL is involved in the origin of atherosclerosis it was subsequently labelled with Tc99m and In-111 as well. A pyrrolidine-methyl-benzamide derivative was separated into its stereoisomers and the active form labelled with I-123. It exhibited specific uptake in Dopamine D-2 receptor containing brain tissue. A benzazepine derivative was likewise labelled with I-123 as potential ligand for D-1 receptors.