Kossut M, Yamada T, Aldrich L B, Pinto L H
Department of Biological Sciences, Purdue University, West Lafayette, IN 47907.
Brain Res. 1989 Jan 2;476(1):78-84. doi: 10.1016/0006-8993(89)91538-2.
We studied the binding of [125I]Tyr11-somatostatin-14 and [125I]Leu8,D-Trp22,Tyr25-somatostatin-28 to frozen, unfixed sections of C57BL/6J mouse eyes with autoradiography. Specific binding of both ligands occurred in 3 maxima, a broad band extending from the retinal ganglion cell to the inner nuclear layers, a narrow and inconstant band over the outer plexiform layer, and a band over the retinal pigment epithelium and choroid. We quantified the label over the inner plexiform layer and found evidence for a single, saturable binding site after Scatchard analysis of saturation binding data. With [125I]Tyr11-somatostatin-14 the dissociation constant (Kd) was 1.48 nM and the total number of binding sites (Bmax) was 68 fmol/mg protein; in competition experiments the inhibitory binding constant (Ki) was 900 pM for somatostatin-14 and 350 pM for somatostatin-28. With [125I]Leu8,D-Trp22,Tyr25-somatostatin-28, Kd was 625 pM and Bmax was 69 fmol/mg protein; in competition experiments Ki was 4.58 nM for somatostatin-14 and 710 pM for somatostatin-28. These results demonstrate the existence of somatostatin receptors in the inner plexiform layer of the retina that appear to have greater specificity for somatostatin-28 than for somatostatin-14.
我们采用放射自显影法研究了[125I]酪氨酸11 - 生长抑素 - 14和[125I]亮氨酸8、D - 色氨酸22、酪氨酸25 - 生长抑素 - 28与C57BL/6J小鼠冷冻、未固定眼部切片的结合情况。两种配体的特异性结合出现在三个最大值处，一条宽带从视网膜神经节细胞延伸至内核层，一条窄且不稳定的带位于外网状层上方，还有一条带位于视网膜色素上皮和脉络膜上方。我们对内核层的标记进行了定量，并在对饱和结合数据进行Scatchard分析后发现了单一、可饱和结合位点的证据。对于[125I]酪氨酸11 - 生长抑素 - 14，解离常数（Kd）为1.48 nM，结合位点总数（Bmax）为68 fmol/mg蛋白质；在竞争实验中，生长抑素 - 14的抑制结合常数（Ki）为900 pM，生长抑素 - 28的为350 pM。对于[125I]亮氨酸8、D - 色氨酸22、酪氨酸25 - 生长抑素 - 28，Kd为625 pM，Bmax为69 fmol/mg蛋白质；在竞争实验中，生长抑素 - 14的Ki为4.58 nM，生长抑素 - 28的为710 pM。这些结果表明视网膜内核层存在生长抑素受体，这些受体对生长抑素 - 28的特异性似乎高于对生长抑素 - 14的特异性。
