USE OF 2-[I-125]IODOMELATONIN TO CHARACTERIZE MELATONIN BINDING-SITES IN CHICKEN RETINA
USE OF 2-[I-125]IODOMELATONIN TO CHARACTERIZE MELATONIN BINDING-SITES IN CHICKEN RETINA
复制标题
DOI：
10.1073/pnas.84.11.3916
复制
发表时间：
1987-06-01
影响因子：
11.1
通讯作者：
TAKAHASHI, JS
中科院分区：
文献类型：
--
作者：
DUBOCOVICH, ML;TAKAHASHI, JS
2-[125 I]碘褪黑激素以高亲和力结合至鸡视网膜膜中具有褪黑激素受体的药理学特征的位点。2-[125 I]碘褪黑素的特异性结合是稳定的、可饱和的和可逆的。饱和实验表明，2-[125 I]碘褪黑激素标记了一类位点，亲和常数（Kd）为434 ± 1。56 pM，结合位点总数（Bmax）为74.0 ± 0.56 pM。13.6 fmol/mg蛋白质。从动力学分析得到的亲和常数与饱和实验中得到的结果非常一致。竞争实验显示2-[125 I]碘褪黑激素结合的顺相减少，具有褪黑激素受体特征性的吲哚胺亲和力的药理学顺序：2-碘褪黑激素> 6-氯褪黑激素。褪黑素≥6，7-二氯-2-甲基褪黑激素> 6-羟基褪黑激素。6-甲氧基褪黑激素> N-乙酰色胺> N-乙酰基-5-羟色胺> 5-甲氧基色胺>5-羟色胺（无活性）。这些褪黑激素类似物在竞争2-[125 I]iodomelatonin结合位点的亲和力与其抑制鸡和兔视网膜[3 H]多巴胺的钙依赖性释放的效力密切相关，表明褪黑激素调节的功能反应的结合位点的关联。结果表明，2-[125 I]iodomelatonin是一种选择性的，高亲和力的放射性配体的褪黑激素受体位点的识别和表征。
2-[125I]Iodomelatonin binds with high affinity to a site possessing the pharmacological characteristics of a melatonin receptor in chicken retinal membranes. The specific binding of 2-[125I]iodomelatonin is stable, saturable, and reversible. Saturation experiments indicated that 2-[125I]iodomelatonin labeled a single class of sites with an affinity constant (Kd) of 434 .+-. 56 pM and a total number of binding sites (Bmax) of 74.0 .+-. 13.6 fmol/mg of protein. The affinity constant obtained from kinetic analysis was in close agreement with that obtained in saturation experiments. Competition experiments showed a monophasic reduction of 2-[125I]iodomelatonin binding with a pharmacological order of indole amine affinities characteristic of a melatonin receptor: 2-iodomelatonin > 6-chloromelatonin .gtoreq. melatonin .gtoreq. 6,7-dichloro-2-methylmelatonin > 6-hydroxymelatonin .gtoreq. 6-methoxymelatonin > N-acetyltryptamine > N-acetyl-5-hydroxtryptamine > 5-methoxytryptamine > > >5-hydroxytryptamine (inactive). The affinities of these melatonin analogs in competing for 2-[125I]iodomelatonin binding sites were correlated closely with their potencies for inhibition of the calcium-dependent release of [3H]dopamine from chicken and rabbit retinas, indicating association of the binding site with a functional response regulated by melatonin. The results indicate that 2-[125I]iodomelatonin is a selective, high-affinity radioligand for the identification and characterization of melatonin receptor sites.