Melanin‐concentrating hormone binding to mouse melanoma cells in vitro

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Abstract
An analogue of human melanin‐concentrating hormone (MCH) suitable for radioiodination was designed in which Tyr13 was replaced by Phe and Val19 by Tyr. The resulting monoiodinated [125I][Phe13,Tyr19]‐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 × 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 α‐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.