Costa L G, Kaylor G, Murphy S D
Department of Environmental Health, University of Washington, Seattle 98195.
Immunopharmacology. 1988 Nov-Dec;16(3):139-49. doi: 10.1016/0162-3109(88)90002-1.
Receptors for neurotransmitters in blood cells could serve as useful markers for the same receptors in solid tissues. Muscarinic receptors have been identified in human, rat and mouse lymphocytes by binding of [3H]quinuclidinyl benzilate (3H-QNB); however, the biochemical and pharmacological characterization of such binding sites has not been complete. Spleen lymphocytes were isolated on a histopaque gradient and incubated in Hank's buffer with 3H-QNB. Binding of 3H-QNB was linear with increasing protein concentrations and was saturable. Binding constants were Bmax = 111 +/- 10.5 fmol/10(6) cells, and Kd = 29.7 +/- 3.9 nM (n = 7). An extensive pharmacological analysis of these binding sites indicated that several cholinergic muscarinic drugs were capable of inhibiting 3H-QNB binding. Muscarinic antagonists were more potent than agonists, and lipophilic drugs were more potent than hydrophilic drugs. Several non-cholinergic drugs were also capable of inhibiting 3H-QNB binding; however, they did so also in brain membranes, while a third group of non-cholinergic drugs and neurotransmitters were inactive. Similar results were also obtained in circulating lymphocytes and in lymphocyte membranes. These results suggest that lymphocytes possess muscarinic receptors which share several, although not all, characteristics of the same receptors in brain and other tissues. Measurement of these binding sites could be useful to monitor the status of muscarinic receptors in solid tissues.
血细胞中的神经递质受体可作为实体组织中相同受体的有用标记物。通过[3H]喹核醇基苯甲酸酯（3H-QNB）的结合，已在人、大鼠和小鼠淋巴细胞中鉴定出毒蕈碱受体；然而，此类结合位点的生化和药理学特性尚未完全明确。在组织培养液梯度上分离脾淋巴细胞，并在含有3H-QNB的汉克缓冲液中孵育。3H-QNB的结合随蛋白质浓度增加呈线性关系且具有饱和性。结合常数为Bmax = 111±10.5 fmol/10(6)个细胞，Kd = 29.7±3.9 nM（n = 7）。对这些结合位点的广泛药理学分析表明，几种胆碱能毒蕈碱药物能够抑制3H-QNB的结合。毒蕈碱拮抗剂比激动剂更有效，亲脂性药物比亲水性药物更有效。几种非胆碱能药物也能够抑制3H-QNB的结合；然而，它们在脑膜中也能如此，而第三组非胆碱能药物和神经递质则无活性。在循环淋巴细胞和淋巴细胞膜中也获得了类似结果。这些结果表明，淋巴细胞拥有毒蕈碱受体，其具有与脑和其他组织中相同受体的若干（尽管不是全部）特征。测量这些结合位点可能有助于监测实体组织中毒蕈碱受体的状态。
