Preparation of neurotensin selectively iodinated on the tyrosine 3 residue. Biological activity and binding properties on mammalian neurotensin receptors

[Monoiodo-Tyr³]neurotensin, a neurotensin analogue that contains a single iodine atom on the side chain of Tyr 3 was prepared and purified. This analogue can be labeled at any specific radioactivity between 0 and 2000 Ci/mmol ; its binding and biological properties on rat and guinea pig neurotensin receptors are identical to those of the parent peptide. These properties make [monoiodo-Tyr³]neurotensin the best suitable radioligand for detection and characterization of neurotensin receptors in various tissues and species.