Stefano G B, Zhao X H, Bailey D, Metlay M, Leung M K
Multidisciplinary Center for the Study of Aging, State University of New York/College at Old Westbury 11568.
J Neuroimmunol. 1989 Jan;21(1):67-74. doi: 10.1016/0165-5728(89)90160-4.
The present report demonstrates that both mouse thymocytes and Mytilus edulis hemocytes contain a novel type of dopamine receptor. Scatchard analysis of these data revealed a single class of high-affinity binding sites with an affinity constant (Kd) of 6.6 nM, and a binding site density (Bmax) of 141 pmol/g protein in mice and a Kd of 7.6 nM and a Bmax of 66 pmol/g protein for the hemocytes. In older Mytilus the Kd was the same; however, there was a significant decrease in the Bmax (48 pmol/g protein; P greater than 0.05). Age changes were not evident for the mouse cells. The ability of a variety of other related drugs to displace specifically bound dopamine was investigated. The catecholamines (norepinephrine greater than epinephrine) and the dopamine agonist epinine were the most potent of the ligands tested and apomorphine and butaclamol were of moderate potency. This may serve to indicate that this dopamine binding site may be very different from the known D1 and D2 sites. This particular site may represent a third type of dopaminergic receptor. Furthermore, the hemocytes of Mytilus appear to be of two major types, namely, cells with a granular cytoplasm and those whose cytoplasm is agranular. Histofluorescence studies on the hemocytes reveal that a subpopulation of the granule-containing cells appears to contain serotonin.
本报告表明，小鼠胸腺细胞和紫贻贝血细胞均含有一种新型多巴胺受体。对这些数据进行Scatchard分析发现，小鼠中有一类高亲和力结合位点，其亲和常数（Kd）为6.6 nM，结合位点密度（Bmax）为141 pmol/g蛋白质；血细胞的Kd为7.6 nM，Bmax为66 pmol/g蛋白质。在较老的紫贻贝中，Kd相同；然而，Bmax显著降低（48 pmol/g蛋白质；P大于0.05）。小鼠细胞未出现明显的年龄变化。研究了多种其他相关药物特异性取代结合多巴胺的能力。儿茶酚胺（去甲肾上腺素＞肾上腺素）和多巴胺激动剂阿扑宁是测试的配体中最有效的，阿扑吗啡和布他拉莫的效力中等。这可能表明该多巴胺结合位点可能与已知的D1和D2位点非常不同。这个特定的位点可能代表第三种类型的多巴胺能受体。此外，紫贻贝的血细胞似乎主要有两种类型，即细胞质有颗粒的细胞和细胞质无颗粒的细胞。对血细胞的组织荧光研究表明，含颗粒细胞的一个亚群似乎含有血清素。
