CHARACTERIZATION OF BENZODIAZEPINE RECEPTORS IN THE BOVINE PINEAL-GLAND - EVIDENCE FOR THE PRESENCE OF AN ATYPICAL BINDING-SITE
CHARACTERIZATION OF BENZODIAZEPINE RECEPTORS IN THE BOVINE PINEAL-GLAND - EVIDENCE FOR THE PRESENCE OF AN ATYPICAL BINDING-SITE
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DOI：
10.1016/0169-328x(86)90004-5
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发表时间：
1986-11-01
期刊：
影响因子：
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通讯作者：
SKOLNICK, P
中科院分区：
文献类型：
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作者：
BASILE, AS;KLEIN, DC;SKOLNICK, P
牛和大鼠松果体苯二氮卓类受体的特征在于使用具有高亲和力的“中央型”（CBR）或“外周型”（PBR）苯二氮卓类受体的配体。特性（Bmax = 83 . ±. 10 fmol/mg蛋白，Kd = 3.88 ±. 0.45用[3 H]氟硝西泮（使用氟硝西泮定义非特异性结合）测定的牛松果体膜中苯二氮卓类受体的浓度（nM）与先前报告的值一致。然而，如果使用Ro 15-1788（选择性CBR配体）定义非特异性结合，[3 H]氟硝西泮的Bmax和Kd分别降低51%和58%。此外，当使用PK 11195测定非特异性结合时，[3 H]氟硝西泮与牛松果体结合的Bmax进一步降低（约80%，Kd降低了约40%。39%）。总之，这些观察结果强烈建议存在PBR的牛松果体。用[3 H]PK 11195表征的牛松果体PBR揭示了高密度（相对于CBR）的高亲和力结合位点（Kd = 1.08 ± 0.01）。0.30，Bmax = 776。33.0 fmol/mg蛋白质）。相反，当[3 H]Ro 5-4864（1-20 nM）用于定义PBR时，未检测到结合。这些观察结果与大鼠松果体形成鲜明对比，在大鼠松果体中[3 H]Ro 5-4864和[3 H]PK 11195均以高亲和力（Kd = 1.000）结合大量PBR。1.9 nM，Bmax近似26 pmol/mg蛋白质）。用结构上与Ro 5-4864或PK 11195相关的化合物进一步表征牛松果体PBR。PK 11195及其2-氟异构体PK 11211都有效地从牛松果体膜上置换[3 H]PK 11195（1 nM）（Ki分别为1.26和1.44 nM），而KW 1937、Ro 5-4864和三唑仑以低亲和力置换[3 H]PK 11195（Ki分别为11.6、9.8和29 μ M）。用Ro 5-6900、KW 1976或溴替唑仑从牛松果体PBR置换[3 H] PK 11195揭示了以4：1的相对密度存在[3 H]PK 11195的高亲和力（Ki分别为229、152和686 nM）和低亲和力（Ki分别为5.00、4.70和4.70 μ M）结合位点。这些结果表明，尽管牛和大鼠松果体的PBR密度大于CBR，但牛松果体PBR的药理学特征与先前在啮齿动物中描述的那些明显不同。
Bovine and rat pineal benzodiazepine receptors were characterized using ligands with high affinities for either ''central-type'' (CBR) or ''peripheral-type'' (PBR) benzodiazepine receptors. The characteristics (Bmax = 83 .+-. 10 fmol/mg protein, Kd = 3.88 .+-. 0.45 nM) of benzodiazepine receptors in bovine pineal membranes measured with [3H]flunitrazepam (using flunitrazepam to define non-specific binding) were consistent with previously reported values. However, if non-specific binding was defined using Ro 15-1788 (a selective CBR ligand), the Bmax and Kd of [3H]flunitrazepam decreased 51 and 58%, respectively. In addition, when using PK 11195 to determine non-specific binding, the Bmax of [3H]flunitrazepam binding to bovine pineal decreased further (.apprxeq. 80%, Kd decreased .apprxeq. 39%). Together, these observations strongly suggested the presence of PBR in the bovine pineal. Bovine pineal PBR characterized with [3H]PK 11195 revealed a high density (relative to CBR) of high affinity binding sites (Kd = 1.08 .+-. 0.30, Bmax = 776 .+-. 33.0 fmol/mg protein). In contrast, when [3H]Ro 5-4864 (1-20 nM) was used to define PBR, no binding was detectable. These observations are in sharp contrast to the rat pineal gland, in which both [3H]Ro 5-4864 and [3H]PK 11195 bind to a large number of PBR with high affinity (Kd .apprxeq. 1.9 nM, Bmax .apprxeq. 26 pmol/mg protein). Bovine pineal PBR were further characterized with compounds structurally related to either Ro 5-4864 or PK 11195. Both PK 11195 and its 2-fluoro isomer PK 11211 potently displaced [3H]PK 11195 (1 nM) from bovine pineal membranes (Ki = 1.26 and 1.44 nM, respectively), while KW 1937, Ro 5-4864 and triazolam displaced [3H]PK 11195 with low affinities (Ki = 11.6, 9.8 and 29 .mu.M, respectively). Displacement of [3H]PK 11195 from bovine pineal PBR by Ro 5-6900, KW 1976 or brotizolam revealed the presence of both high (Ki = 229, 152 and 686 nM, respectively) and low affinity (Ki = 5.00, 4.70 and 4.70 .mu.M, respectively) binding sites for [3H]PK 11195 at a relative density of 4:1. These results indicte that although both the bovine and rat pineal gland have a greater density of PBR than CBR, the pharmacological characteristics of bovine pineal PBR are markedly different from those previously described in rodents.