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)]-MCH radioligand was biologically active and led to the discovery of high-affinity binding sites on mouse B16-F1, G4F and G4F-7 melanoma cells. Saturation binding analysis with G4F-7 cells revealed 1090 MCH receptors per cell and a K-D of 1.18 x 10(-10) mol/l. Receptors for MCH were also found on rat PC12 phaeochromocytoma cells, human RE melanoma cells and COS-7 cells. Competition binding analyses with other peptides such as alpha-MSH, NPY and PACAP demonstrated that MCH receptor binding is specific, rANF(1-28) was found to be a weak competitor of MCH, indicating topological similarities between MCH and rANF(1-28) when interacting with MCH receptors.