MELANIN-CONCENTRATING HORMONE-BINDING TO MOUSE MELANOMA-CELLS IN-VITRO

An analogue of human melanin-concentrating hormone (MCH) suitable for radioiodination was designed in which Tyr(13) was replaced by Phe and Val(19) by Tyr. The resulting monoiodinated [I-125][Phe(13),Tyr(19)]-M CH radioligand was biologically active and led to the discovery of hig h-affinity binding sites on mouse B16-F1, G4F and G4F-7 melanoma cells . Saturation binding analysis with G4F-7 cells revealed 1090 MCH recep tors per cell and a K-D of 1.18 x 10(-10) mol/l. Receptors for MCH wer e also found on rat PC12 phaeochromocytoma cells, human RE melanoma ce lls and COS-7 cells. Competition binding analyses with other peptides such as alpha-MSH, NPY and PACAP demonstrated that MCH receptor bindin g is specific, rANF(1-28) was found to be a weak competitor of MCH, in dicating topological similarities between MCH and rANF(1-28) when inte racting with MCH receptors.