Huo T, Healy D P
Department of Pharmacology, Mount Sinai School of Medicine, City University of New York, New York.
J Pharmacol Exp Ther. 1991 Aug;258(2):424-8.
Previous studies by our laboratory have indicated that inner medullary collecting ducts (IMCDs) express a novel dopamine (DA) receptor, designated DA2K, that is linked to stimulation of prostaglandin E2 production. This receptor has a distinct pharmacological profile and is similar in size, but not homologous to, the brain D2 receptor. Because the DA2-selective antagonist domperidone blocks DA-mediated stimulation of prostaglandin E2 production in IMCD cells, we utilized [3H]domperidone to study the binding characteristics of the DA2K receptor in IMCD cells. [3H]Domperidone binding was saturable and best fit to a single high density site (KD, 57.6 +/- 10.5 nM; Bmax, 14.9 +/- 2.7 pmol/mg protein). The specificity of [3H]domperidone binding in IMCD cells was verified by competition analysis with a variety of dopaminergic and nondopaminergic agents. Dopaminergic drugs were less potent competitors for [3H]domperidone binding in IMCD cells than previously reported for brain DA receptors, but the rank order was consistent with the labeling of a DA receptor [antagonists: domperidone greater than spiperone greater than haloperidol greater than Sch 23390 much greater than (-)-sulpiride; agonists: norapomorphine greater than fenoldopam much greater than dopamine = quinpirole], and was better correlated with the pharmacological profile for the brain D2 receptor than the brain D3 receptor. In addition, quinpirole, the most D3-selective ligand currently available, did not compete for [3H]domperidone binding in IMCD cells. These results add further support to the existence of a novel high density DA receptor, DA2K, expressed in IMCD cells.
我们实验室之前的研究表明，髓质内集合管（IMCDs）表达一种新型多巴胺（DA）受体，命名为DA2K，它与前列腺素E2生成的刺激作用相关联。该受体具有独特的药理学特征，大小与脑D2受体相似，但二者并非同源。由于DA2选择性拮抗剂多潘立酮可阻断IMCD细胞中DA介导的前列腺素E2生成刺激作用，我们利用[3H]多潘立酮来研究IMCD细胞中DA2K受体的结合特性。[3H]多潘立酮结合具有饱和性，最适合单一高密度位点（KD，57.6±10.5 nM；Bmax，14.9±2.7 pmol/mg蛋白）。通过与多种多巴胺能和非多巴胺能药物进行竞争分析，验证了IMCD细胞中[3H]多潘立酮结合的特异性。多巴胺能药物在IMCD细胞中对[3H]多潘立酮结合的竞争效力低于先前报道的脑DA受体，但竞争顺序与DA受体的标记一致[拮抗剂：多潘立酮＞螺哌隆＞氟哌啶醇＞Sch 23390＞（-）舒必利；激动剂：去甲阿朴吗啡＞非诺多泮＞多巴胺 = 喹吡罗]，并且与脑D2受体的药理学特征比脑D3受体的相关性更好。此外，目前可得的最具D3选择性的配体喹吡罗，在IMCD细胞中不竞争[3H]多潘立酮结合。这些结果进一步支持了IMCD细胞中存在一种新型高密度DA受体DA2K。
