Synthesis and characterization of iodinated vasopressin antagonists which retain high affinity for the vasopressin...

The mono- and di-iodinated analogs of lysine and arginine vasopressin have been prepared previously but not well characterized chemically. Their biological activities are greatly reduced with respect to LVP or AVP. In this paper we report a convenient synthesis of iodinated AVP agonists and antagonists, their purification by high performance liquid chromatography, and their characterization by fast atom bombardment mass spectrometry. In contrast to the results obtained with agonists, the mono-iodinated vasopressin antagonist retains virtually the full receptor activity of its non-iodinated parent. This should allow the preparation of labeled vasopressin antagonists of high specific activity for receptor characterization and isolation.