Piwko C, Thoss V S, Probst A, Hoyer D
Preclinical Research, SANDOZ Pharma Ltd, Basel, Switzerland.
Neuropharmacology. 1996 Jun;35(6):713-23. doi: 10.1016/0028-3908(96)84643-0.
Radioligand binding studies were performed in membranes of human cerebellum using [125I][Tyr3]octreotide also known as [125I]204-090, [125I]LTT-SRIF-28 ([Leu8, D-Trp22, 125I-Tyr25]SRIF-28) and [125I]CGP 23996 ([125I]c[Asu-Lys-Asn-Phe-Trp-Lys-Thr-Tyr-Thr-Ser]) to characterize the nature of cerebellar somatostatin receptors. Saturation experiments performed with [125I]204-090 suggest the presence of a single class of binding sites with high affinity: Bmax = 55.7 +/- 9.7 fmol/mg protein, pKd = 9.57 +/- 0.04. The pharmacological profile of [125I]204-090 and [125I]LTT-SRIF-28 labelled sites in human cerebellar membranes was overlapping (correlation coefficient r = 0.998) and correlated very significantly with that of recombinant human sst2 receptors (r = 0.987). By contrast, there was very little correlation with those of recombinant human sst3 (r = 0.208) or human sst5 receptors (r = 0.547). In contrast to [125I]204-090 or [125I]LTT-SRIF-28 binding, [125I]CGP 23996 binding (in 5 mM MgCl2 buffer) in cerebellar membranes was heterogeneous as indicated by biphasic competition curves produced by sst2 receptor selective ligands such as seglitide or octreotide. The pharmacological profile of the major component was closely correlated with that of human sst2 receptors (r = 0.989), whereas the minor component correlated equally well with human sst1 or sst4 receptors (r = 0.902 and 0.941, respectively). In vitro autoradiographic studies performed in cerebellar slices using [125I]204-090 and [125I]LTT-SRIF-28 demonstrated the presence of binding sites predominantly in the molecular layer, whereas weaker labelling was detected in the granular layer. The distribution of sites labelled by both radioligands was very similar. Using [125I]CGP 23996 (in 120 mM NaCl buffer), no clear difference between labeling of the molecular and granular layers was detectable; the dentate nucleus demonstrated binding sites for [125I]CGP 23996, in contrast to the very low level of binding observed with both, [125I]204-090 and [125I]LTT-SRIF-28. Together, the present data demonstrate the presence of SRIF receptors in the adult human cerebellar cortex which are, for the major population, best characterized as sst2. The SRIF receptors in the minor populations of the cerebellar cortex and the dentate nucleus most probably represent sst1 and/or sst4 sites.
使用[125I][Tyr3]奥曲肽（也称为[125I]204 - 090）、[125I]LTT - SRIF - 28（[亮氨酸8，D - 色氨酸22，125I - 酪氨酸25]SRIF - 28）和[125I]CGP 23996（[天冬酰胺 - 赖氨酸 - 天冬酰胺 - 苯丙氨酸 - 色氨酸 - 赖氨酸 - 苏氨酸 - 酪氨酸 - 苏氨酸 - 丝氨酸]）在人小脑膜中进行放射性配体结合研究，以表征小脑生长抑素受体的性质。用[125I]204 - 090进行的饱和实验表明存在一类具有高亲和力的单一结合位点：Bmax = 55.7±9.7 fmol/mg蛋白质，pKd = 9.57±0.04。[125I]204 - 090和[125I]LTT - SRIF - 28在人小脑膜中标记位点的药理学特征重叠（相关系数r = 0.998），并且与重组人sst2受体的特征非常显著相关（r = 0.987）。相比之下，与重组人sst3（r = 0.208）或人sst5受体（r = 0.547）的相关性非常小。与[125I]204 - 090或[125I]LTT - SRIF - 28结合不同，小脑膜中[125I]CGP 23996的结合（在5 mM MgCl2缓冲液中）是异质性的，如司格列肽或奥曲肽等sst2受体选择性配体产生的双相竞争曲线所示。主要成分的药理学特征与人类sst2受体密切相关（r = 0.989），而次要成分与人类sst1或sst4受体的相关性同样良好（分别为r = 0.902和0.941）。使用[125I]204 - 090和[125I]LTT - SRIF - 28在小脑切片中进行的体外放射自显影研究表明，结合位点主要存在于分子层，而在颗粒层中检测到较弱的标记。两种放射性配体标记的位点分布非常相似。使用[125I]CGP 23996（在120 mM NaCl缓冲液中），分子层和颗粒层的标记之间没有明显差异；齿状核显示出[125I]CGP 23996的结合位点，这与用[125I]204 - 090和[125I]LTT - SRIF - 观察到的非常低的结合水平形成对比。总之，目前的数据表明在成人人类小脑皮质中存在生长抑素受体，对于主要群体而言，其最佳特征为sst2。小脑皮质和齿状核次要群体中的生长抑素受体很可能代表sst1和/或sst4位点。
