PREPARATION OF TRITIATED α-MELANOTROPIN WITH HIGH SPECIFIC RADIOACTIVITY

α-Metanotropin (α-MSH) was iodinated and 3,5-diiodotyr² -α-MSH was isolated by reverse phase high performance liquid chromatography (HPLC). Catalytic dehalogenation of the diiodo derivative in the presence of tritium resulted in the formation of 3,5-ditritiotyr² -α-MSH. The tritiated peptide was purified by ion exchange and partition chromatography. The radioactive peptide was found to be homogeneous and identical to α-MSH by paper electrophoresis and HPLC. The tritiated α-MSH stimulated lipolysis in rabbit adipocytes nearly as well as α-MSH. The specific radioactivity of tritiated α-MSH was 42 Ci/mmol or 73% of the theoretical value.