Hintermann E, Drozdz R, Tanner H, Eberle A N
Department of Research (ZLF), University Hospital, Basel, Switzerland.
J Recept Signal Transduct Res. 1999 Jan-Jul;19(1-4):411-22. doi: 10.3109/10799899909036661.
Melanin-concentrating hormone (MCH) is a neuropeptide present in the brain of all vertebrates. For the characterization of MCH receptors, a monoiodinated [Phe13, Tyr19]-MCH radioligand analogue was developed. The high susceptibility of [125I]-[Phe13, Tyr19]-MCH to oxidative damage and its very lipophilic nature made it necessary to develop new MCH radioligands. To increase the stability, native methionines were replaced by non-sulphur containing amino acid residues. In one analogue, the L-enantiomer of the phenylalanine residue at position 13 was substituted by the D-enantiomer, which increased the relative affinity of the ensuing [125I]-[D-Phe13, Tyr19]-MCH about 7-fold. The different analogues were iodinated by an enzymatic reaction and used for binding studies with mouse melanoma cells. [125I]-[Met(O)4,8, Phe13, Tyr19]-MCH and [125I]-[Hse4,8, Phe13, Tyr19]-MCH showed only about 19% of total binding and [125I]-[Ser4,8, Phe13, Tyr19]-MCH displayed about 44% of total binding when compared with [125I]-[Phe13, Tyr19]-MCH. Non-specific binding for all tracers was below 11% of total binding of [125I]-[Phe13, Tyr19]-MCH binding. [125I]-[D-Phe13, Tyr19]-MCH was used for saturation binding studies and revealed a KD of 122.7 +/- 15.3 pmol/l. This radioligand was further characterized by association and dissociation binding studies.
黑色素浓缩激素（MCH）是一种存在于所有脊椎动物大脑中的神经肽。为了对MCH受体进行表征，开发了一种单碘化的[苯丙氨酸13，酪氨酸19]-MCH放射性配体类似物。[125I]-[苯丙氨酸13，酪氨酸19]-MCH对氧化损伤的高敏感性及其极强的亲脂性使得开发新的MCH放射性配体成为必要。为了提高稳定性，将天然甲硫氨酸替换为不含硫的氨基酸残基。在一种类似物中，第13位苯丙氨酸残基的L-对映体被D-对映体取代，这使得随后的[125I]-[D-苯丙氨酸13，酪氨酸19]-MCH的相对亲和力提高了约7倍。不同的类似物通过酶促反应进行碘化，并用于与小鼠黑色素瘤细胞的结合研究。与[125I]-[苯丙氨酸13，酪氨酸19]-MCH相比，[125I]-[甲硫氨酸（O）4,8，苯丙氨酸13，酪氨酸19]-MCH和[125I]-[硒代半胱氨酸4,8，苯丙氨酸13，酪氨酸19]-MCH仅显示约19%的总结合，而[125I]-[丝氨酸4,8，苯丙氨酸13，酪氨酸19]-MCH显示约44%的总结合。所有示踪剂的非特异性结合低于[125I]-[苯丙氨酸13，酪氨酸19]-MCH结合总结合的11%。[125I]-[D-苯丙氨酸13，酪氨酸19]-MCH用于饱和结合研究，结果显示解离常数（KD）为122.7±15.3 pmol/l。该放射性配体通过结合和解离结合研究进一步表征。
