基于报告基因检测的PXR、FXR和LXRα激动剂高通量筛选模型的建立

目的建立基于报告基因法的高通量筛选细胞模型,用来发现PXR、FXR和LXRα受体激动剂。方法利用Real-time定量PCR方法比较HEK293、Hep G2和LS174T细胞中内源性核受体PXR、FXR和LXRα的表达量,将p SG5-h PXR和p GL3-XREM-CYP3A4、p EGFP-N3-h FXR和EcRETK-Luc、p CMX-FLAG-h LXRα和p GL3-XREM-CYP3A4等质粒分别共转染到工具细胞中,优化共转染比例,并考察阳性药与萤光素酶报告基因表达强度的量效关系、模型特异性和稳定性。结果 1根据Real-time定量PCR结果,模型选用低表达PXR、FXR和LXRα的HEK293细胞作为工具细胞;2根据不同共转染比例对报告基因活性的结果,PXR、FXR和LXRα报告基因药物筛选模型的报告基因和过表达质粒比例,最终分别选择1∶1、2∶1和2∶1;3模型中,报告基因活性均与相应阳性药物(PXR/Rif、FXR/CDCA和LXRα/T0901317)呈剂量依赖性增长;4仅PXR激动剂Rif、FXR激动剂CDCA和LXRα激动剂T0901317可分别明显增加相应筛选模型的报告基因活性,分别重复5次试验后,计算得Z'值分别为0.58、0.66和0.63。结论该研究建立的PXR、FXR和LXRα激动剂高通量筛选模型,具有良好的特异性和稳定性,适用于对PXR、FXR和LXRα受体激动剂的筛选,进而开发以核受体作为药物靶点的药物。     

糖尿病致病基因醛糖还原酶基因及其抑制剂筛选模型的构建及功能研究

目的基因工程方法建立人醛糖还原酶基因(AR)的蛋白分子模型,并将该模型应用于中草药AR抑制剂的初步筛选。方法将含基因AR及融合基因AR∷GFP的重组质粒pcDNA3.1/myc-His-AR及pcDNA3.1/myc-His-AG瞬时转染HEK293细胞,分别命名为HAR、HAG细胞株。通过荧光显微镜观察AR∷GFP的绿色荧光直接判断转染效果及估计基因AR的表达;Western blot、紫外分光光度法检测AR蛋白表达及AR酶活性。应用此HAR模型对黄芩苷等5种中草药进行初步筛选,并与经典AR抑制剂Sorbinil、Zopolrestat的抑制效果比较。结果GFP绿色荧光表达丰富,表明质粒转染效率较高;Western blot和紫外分光光度法显示:转染后HEK293细胞中AR蛋白表达量高,AR酶活性强(空白对照的2.5倍)。AR抑制剂筛选实验揭示,黄芩苷、虎杖苷、蕨麻多糖JM等中草药表现出与Sorbinil相近的AR抑制活性。结论AR的蛋白分子模型成功建立,此模型可得到较大量高活性AR酶蛋白,并可应用于AR抑制剂的初步稳定筛选;黄芩苷、虎杖苷、蕨麻多糖JM等中草药显示出潜在的AR抑制活性。     

A cell model for high-throughput screening GLP-1 receptor agonists北大核心CSCD

目的构建GLP-1受体激动剂高通量筛选细胞模型。方法构建pEGFP-GLP-1R-3C重组质粒,转染HEK293T细胞,用G418和流式细胞仪进行筛选。所构建的细胞系命名为HEK293T-GLP-1R-3C-eGFP细胞系。Western blot和激光共聚焦检测GLP-1R-3C-eGFP蛋白的表达。将环磷酸腺苷(cyclic adenosine monophosphate,cAMP)响应元件报告基因转染HEK293T-GLP-1R-3C-eGFP细胞,不同浓度的GLP-1刺激后,用一步法荧光素酶报告基因检测试剂盒检测发光值反映细胞cAMP水平,采用cAMP试剂盒(ELISA)进行验证。结果成功构建HEK293T-GLP-1R-3C-eGFP细胞系。不同浓度GLP-1刺激后,发光值变化趋势与细胞cAMP水平变化趋势相似。本实验中Z′因子的值为0.52。结论本研究建立了基于重组HEK293T细胞株,其可用于GLP-1受体激动剂高通量筛选。     

基于报告基因和PPARγ信号通路的药物筛选模型的建立

目的　建立基于报告基因和PPARγ(peroxisomeprolif erator activatedreceptorγ)信号通路的药物筛选模型,用此模型筛选具有胰岛素增敏活性的小分子化合物。方法　五种细胞分别进行瞬时转染,将含有目的片段PPRE(peroxisomeproliferatorresponseelement)和报告基因荧光素酶(Luc)的质粒及表达PPARγ的质粒共转染到细胞中,通过测定荧光素酶活力来考察马来酸罗格列酮对PPARγ信号通路的影响,选取诱导表达倍数最高的细胞株建立模型。用其他类型核受体激动剂对此模型进行特异性考察。结果　293T细胞中,荧光素酶的表达受马来酸罗格列酮的诱导倍数最高,可达4 9倍,并呈现一定的剂量依赖关系,Z′因子为0 .72。而其他各类核受体激动剂的诱导表达率均在1倍左右。马来酸罗格列酮在转染剂量范围内无促进细胞增殖的作用。结论　马来酸罗格列酮对共转染报告基因质粒和表达PPARγ质粒的293T细胞Luc的表达具有较强的诱导作用,此模型具有较好的特异性和稳定性,适用于建立筛选PPARγ激动剂的高通量筛选模型。     

毒蕈胆碱M_1受体激动剂的高通量筛选模型

目的　建立毒蕈碱样胆碱M1 受体激动剂的高通量筛选模型 ,以此模型进行M1 受体激动剂筛选。方法　将M1 受体基因质粒 (M1 /pCDNA3 1 )与报告基因质粒 (3×CRE/ 3×MRE/SRE LUC)按 1∶5的比例共转染HEK2 93 ,建立了一个稳定的M1 受体激动剂报告基因筛选细胞株。配体与细胞表面M1 受体结合后 ,激活相应的信号通路 ,调节报告基因的表达 ,通过测定荧光酶素报告基因表达水平的变化 ,评估配体激活M1 受体的生物活性。结果　通过对筛选条件 ,如细胞数目、荧光素酶表达时间、底物浓度的优化 ,建立了可靠的筛选方法 ,并对多种抗衰老中药水提物进行了筛选 ,找到 3种对M1 受体有活性的中药。结论　该系统能准确、稳定、有效地应用于M1 受体激动剂的高通量筛选     

GLP-1R激动剂的细胞筛选模型的建立

目的构建靶向GLP-1R的高通量筛选模型。方法构建过表达GLP-1R的重组质粒和响应GLP-1信号通路的报告载体,共转染到HEK293细胞中,筛选得到稳定转染的单克隆细胞株,并用阳性药进行模型验证。结果成功构建了表达GLP-1R的重组质粒pcDNA3.1(+)-HuGLP-1R和响应GLP-1信号通路的报告载体PGL4.22-CRE-vip-GFP,共转染到HEK293细胞,筛选得到稳定转染细胞株CG-HEK293,经GLP-1刺激后,确定GFP的最佳表达时间为8 h,经过不同浓度的GLP-1刺激后,能够剂量依赖性地激活GFP的表达。结论构建了靶向GLP-1R的高通量筛选模型,该模型能够直观、稳定、高通量的筛选靶向GLP-1R的小分子或者GLP-1类似物,为长效的GLP-1类似物的研究和开发奠定了基础。     

CYP1A1体外诱导活性评价模型的建立及其在人参皂苷筛选中的应用

目的 建立hAhR介导的CYP1A1体外诱导活性评价模型,应用于体外快速筛选通过hAhR途径介导的对CYP1A1具有激活能力的药物。方法 利用双荧光素酶报告基因系统,将CYP1A1启动子序列插入报告基因质粒上游,构建pGL4.17-CYP1A1质粒,并与含有hAhR编码区序列的pcDNA3.1-hAhR表达质粒瞬时共转染HepG2细胞, pGL4.17-control、pcDNA3.1（+）分别为pGL4.17-CYP1A1、pcDNA3.1-hAhR的空载体,建立hAhR-CYP1A1报告基因模型;应用AhR的完全激动剂TCDD（2 nmol/L）验证该报告基因模型的可靠性,应用该模型考察人参皂苷Rf、Rc、Re、Rg₁、Rb、Rd、Rh₂和Rg₃（20 μmol/L）通过hAhR途径对CYP1A1的诱导作用。结果 经验证,报告基因模型构建成功;人参皂苷Rf、Re、Rg₁和Rc对AhR具有激活作用,其中与对照组比较,人参皂苷Rg₁、Rc对AhR激活效应显著（P<0.05、0.01）,人参皂苷Rb、Rd、Rh₂和Rg₃对AhR无激活作用。结论 本研究建立基于hAhR的CYP1A1体外诱导活性评价模型,可为具有潜在CYP1A1诱导作用的目标化合物的筛选提供有效、快速的体外筛选手段,人参皂苷Rg₁、Rc对AhR-CYP1A1激活效应显著。     

基于报告基因的PPAR-α激动剂筛选体系的建立

目的基于PPAR-α受体的信号传递通路和利用双萤光素酶报告基因分析方法,建立稳定的PPAR-α激动剂体外筛选体系。方法 pcDNA3.1-PPAR-α、pGL3-PPRE-luc及pRL-CMV共转染293T细胞后,设0,0.1,1,10,50μmol·L-1非诺贝特不同浓度点进行干预后,测定每浓度点重复5个样本。对转染优化试验数据,比较均值大小选取最佳结果;对不同转染组之间的差异性比较,采用t检验和方差分析。结果浓度为0.1,1,10,50μmol·L-1非诺贝特干预组相对诱导率分别为：0.82,1.29,1.72,1.94,表现有统计学差异（P〈0.05）。结论成功建立基于PPAR-信号通路及双萤光素酶报告基因分析方法的PPAR-α激动剂筛药系统。     

基于报告基因检测的β3肾上腺素受体激动剂筛选模型的建立与应用

目的：建立基于双荧光素酶报告基因检测的β3肾上腺素受体（β3-AR）激动剂筛选模型,并用于β3-AR激动剂的筛选。方法：应用免疫细胞化学法鉴定β3-AR在β3-CHO细胞上的稳定表达,并将pCRE-luc质粒与pRL-TK质粒共同瞬时转染β3-CHO细胞,建立一种基于双荧光素酶报告基因检测的β3-AR激动剂筛选模型。通过检测报告基因萤火虫荧光素酶与海肾荧光素酶活性的比值,来间接反映配体对β3-AR的激动活性。并以β-AR激动剂异丙肾上腺素刺激对模型的有效性进行验证,在此基础上以此模型对20种新化合物的β3-AR激动活性进行筛选。结果：β3-CHO细胞经免疫细胞化学法鉴定有特异性受体蛋白表达。通过将两个报告基因质粒转染该细胞后,与加入溶剂对照相比,加入异丙肾上腺素可显著促进荧光素酶报告基因的表达,表明该模型有效、可靠。以此模型从20个化合物中初筛出8个活性较强的β3-AR激动剂。结论：本研究建立了基于双荧光素酶报告基因检测的β3-AR激动剂筛选模型,并以此模型筛选发现了几个活性较强的β3-AR激动剂。     

副黏病毒Tianjin株NP蛋白的稳定表达及其检测

目的:构建副黏病毒Tianjin株NP基因的真核表达载体,转染HEK293细胞,经G418筛选出稳定表达NP蛋白的细胞.方法:应用RT-PCR技术克隆副黏病毒Tianjin株NP基因,插入真核表达载体pcDNA3.1(+).经PCR、酶切和测序鉴定后,将构建的pcDNA3.1(+)-NP用LipofectaminenTM2000转染试剂转染HEK293细胞.应用免疫荧光法及Western Blot检测NP蛋白的瞬时和稳定表达.结果:RT-PCR扩增得到NP基因,重组质粒pcDNA3.1(+)-NP转染HEK293细胞后,经免疫荧光法检测到目的蛋白的瞬时和稳定表达.Western Blot法可见NP蛋白瞬时和稳定表达的条带.结论:副黏病毒Tianjin株NP基因在HEK293细胞可以瞬时和稳定表达,为研究副黏病毒Tianjin株NP蛋白功能与病毒致病性、宿主亲嗜性奠定了基础.     

真核表达质粒pcDNA3.1(+)-h/mCD44v6的构建和鉴定

目的构建含人/鼠嵌合粘附分子CD44拼接变异体6(chimeric human and mouse CD44 splice variant 6,h/mCD44v6)基因真核表达质粒pcDNA3.1(+)-h/mCD44v6,并进行表达。方法通过PCR扩增h/mCD44v6的全基因cDNA,将扩增的cDNA克隆至PGM-Teasy,测序后插入pcD-NA3.1(+)真核表达质粒,构建重组真核表达质粒pcD-NA3.1(+)-h/mCD44v6,经限制内切酶酶切分析及测序鉴定后,用脂质体转染B16细胞,通过RT-PCR扩增出B16/pcDNA3.1(+)-h/mCD44v6细胞株中h/mCD44v6全段基因cDNA。结果经4轮PCR,成功扩增出h/mCD44v6的cD-NA全长基因,成功构建了真核表达质粒pcDNA3.1(+)-h/mCD44v6,通过RT-PCR方法证实该质粒能在B16真核细胞中正确表达;建立了稳定的细胞株B16/pcDNA3.1(+)-h/mCD44v6。结论成功克隆和构建了h/mCD44v6的真核表达质粒pcDNA3.1(+)-h/mCD44v6,为进一步研究h/mCD44v6的新功能和免疫治疗奠定了基础。     

Development of a sensitive and HTS-compatible reporter gene assay for functional analysis of human adenosine A2a receptors in CHO-K1 cells

Adenosine A2a receptor, a member of the G protein-coupled receptor superfamily, has been demonstrated to be an important pharmacological target. It couples to stimulatory G protein and activates adenylate cyclase upon agonist stimulation. Here we attempted to stably transfect Chinese hamster ovary (CHO-K1) cells, which lack any known subtypes of adenosine receptors, with recombinant human adenosine A2a receptors (hA2aR). Rapid down-regulation of hA2aR in a clonal cell line, CHOA2a-2, was observed over a short period of time in culture. This is consistent with other groups' findings of low expression and poor G protein coupling of this receptor in several cell systems. To facilitate pharmacological profiling for hA2aR ligand, we introduced a cyclic AMP response element (CRE)-linked beta-galactosidase reporter gene into CHOA2a-2 cells to generate a stable cell line, CHOA2a-2CREbetagal#26. Robust cyclic AMP signal amplification was obtained using a colorimetric assay measuring beta-galactosidase activity. The EC(50) of 5'-N-ethylcarboxamidoadenosine (NECA), a potent A2a agonist, for inducing beta-galactosidase activity was 23.3 +/- 3.5 nM, similar to 22.7 +/- 3.9 nM, which was the NECA EC(50) in the direct measurement of cyclic AMP of CHOA2a-2 cells in early culture. Subsequently we validated this assay for high throughput screening for hA2aR agonists. The Z' factor for robotic assay performance was 0.79 +/- 0.03, the ratio of signal/noise was 157 +/- 36, and the ratio of signal/background was 10.6 +/- 1.2, demonstrating that this assay is well suitable for quality high throughput screening. High throughput screening of Johnson & Johnson libraries uncovered a couple of distinct series of nonadenosine small molecules, in addition to adenosine analogues, as potential hA2aR agonists with EC(50) values of 2-6 microM. Preliminary characterization of those compounds was presented.     

Stable expression of adenylyl cyclase 2 leads to the functional rescue of human 5-HT6 receptor in a CHODUKX cell line

INTRODUCTION: The generation and selection of recombinant cell lines specifically designed to express high picomolar levels of heterologous G-protein-coupled receptors can lead to loss of ligand-dependent functional activity. As a result, the clonal selection of a suitable host model and/or lower receptor expression levels within the same cell system becomes important especially when a functional assay is necessary to evaluate the pharmacological potencies of ligands at the receptor site. To address this question, we examined the utility of various signal transducers to restore the functional capacity of a high expressing human 5-HT(6) receptor CHODUKX system. METHODS: The plasmids for human 5-HT(6) receptor and full-length human G(s), G(olf) and rat adenylyl cyclase isoforms 2 (rAC2) and 5 were obtained by PCR. The h5-HT(6) receptor pHTop plasmid was stably transfected into a CHODUKX cell line to generate an h5-HT(6) expressing clone. h5-HT(6) CHODUKX cells were transfected with signaling components and functional cAMP responses measured. rAC2 was selected to generate a double stable h5-HT(6) receptor/rAC2 pHTop CHODUKX line. RESULTS: The h5-HT(6) receptor CHODUKX line was a high receptor expressor (>2 pmol/mg protein) but an extremely poor ligand-dependent functional responder, failing to produce the appropriate cAMP signal upon addition of selective agonists. We found that stable co-expression of rAC2 with h5-HT(6) receptor in the CHODUKX cell line displayed dose-dependent cAMP accumulation following agonist treatment. The pharmacological profile of several agonists in the h5-HT(6) receptor/rAC2 cell line was consistent with an h5-HT(6)-like receptor-mediated event. DISCUSSION: We provide evidence for restoration of functional capacity in a heterologous G(s)-coupled 5-HT(6)/AC2 CHODUKX expression system. We discuss the broader value of a stable AC2-expressing CHODUKX cell line in which the generation of high expressing GPCR receptor/AC2 lines can retain their functional responsiveness and provide pharmacological drug comparisons between the same host line for screening purposes and measurement of multiple cellular parameters.     

Pharmacology of cloned human 5-HT1D receptor-mediated functional responses in stably transfected rat C6-glial cell lines: further evidence differentiating human 5-HT1D and 5-HT1B receptors

This study was undertaken to investigate the pharmacology of human serotonin (5-HT)_1D receptor sites by measuring two functional cellular responses, inhibition of forskolin-stimulated cAMP formation and promotion of cell growth, using transfected rat C6-glial cell lines and a broad series of 5-HT receptor agonists. Stable and separate transfection of a pcDNA3 or pRcRSV plasmid, each containing a cloned human 5-HT_1D receptor gene, in rat C6-glial cells was confirmed with RT PCR of 5-HT_1D receptor mRNA and radioligand binding with [³H] 5-carboxamidotryptamine (5-CT) and [³H] sumatriptan. The 5-HT_1D receptor density was 350 and 1050 fmol/mg protein for the C6-glial/pcDNA3/5-HT_1D and C6-glial/pRcRSV/5-HT_1D cell line, and forskolin (100 M)-induced cAMP formation was inhibited by 45 and 78% in the presence of 1 M 5-HT, respectively. A comparison of the intrinsic agonist activities for sixteen 5-HT receptor ligands with their corresponding binding affinities for the human 5-HT_1D receptor site showed similar results for both cell lines with the exception of the partial agonist m-trifluoro-phenyl-piperazine (TFMPP). Three classes of compounds were observed: 1. efficacious agonists, such as 5-CT, 5-methoxytryptamine, 5-HT, sumatriptan, bufotenine, 5-methoxy-3(1,2,3,6-tetrahydro-4-pyridinyl)1H-indole (RU 24,969), tryptamine and 8-hydroxy-2(di-n-propilamino)tetralin (8-OH-DPAT), with agonist potency close to their binding affinity; 2. the partial agonists metergoline, 7-trifluoromethyl-4(4-methyl-l-piperazinyl)-pyrolo-(1,2-a) quinoxaline (CGS 12066B), 1-naphthylpiperazine and 2-methyl-4-(5-methyl-[1,2,4]oxadiazol-3-yl)-biphenyl-4-carboxylic acid [4-methoxy-3-(4-methylpiperazin-1-yl)-phenyl]-amide (GR 127,935) with marked intrinsic agonist activity but at concentrations higher than their binding affinity; and 3. the silent antagonists ritanserin, ketanserin and methiothepin, apparently free of intrinsic agonist activity, with antagonist potency close to their binding affinity. The cAMP data were further supported by the observed promotion of cell growth by stimulation of both transfected cell lines with sumatriptan under serum-free conditions; half-maximal stimulation was obtained at 4.4 nM (C6-glial/pcDNA3/5-HT_1D) fully in agreement with its EC₅₀-value (5.7 nM) for inhibition of cAMP formation. This growth promoting effect was antagonised by 1 M methiothepin and not observed in pcDNA3-plasmid-transfected and non-transfected C6-glial cells. A comparative study with a C6-glial/pcDNA3/5-HT_1B cell line expressing a similar amount of cloned human 5-HT_1B receptors (B _max: 360 fmol/mg protein) showed almost no intrinsic agonist activity for metergoline, 1-naphtylpiperazine and GR 127,935. Together with the 5-HT_1D receptor binding selectivity and antagonist activity of ketanserin and ritanserin, the findings define important pharmacological differences between cloned human 5-HT_1D and 5-HT_1B receptor sites.     

Serotonergic drugs : effects on appetite expression and use for the treatment of obesity

Over 35 years of research suggests that endogenous hypothalamic serotonin (5-hydroxytryptamine) plays an important part in within-meal satiation and post-meal satiety processes. Thus, the serotonin system has provided a viable target for weight control, critical to the action of at least two effective anti-obesity treatments, both producing clinically significant weight loss over a year or more. Numerous serotonin receptor subtypes have been identified; of these, serotonin 5-HT1B and 5-HT2C receptors have been specifically recognised as mediators of serotonin-induced satiety.A number of serotonergic drugs, including selective serotonin reuptake inhibitors (SSRIs), dexfenfluramine and 5-HT2C receptor agonists, have been shown to significantly attenuate rodent bodyweight gain. This effect is strongly associated with marked hypophagia and is probably mediated by the hypothalamic melanocortin system. Additionally, sibutramine, dexfenfluramine, fluoxetine and the 5-HT2C receptor agonist chlorophenylpiperazine (mCPP) have all been shown to modify appetite in both lean and obese humans, resulting in reduced caloric intake. Clinical studies demonstrate serotonergic drugs specifically reduce appetite prior to and following the consumption of fixed caloric loads, and cause a reduction in pre-meal appetite and caloric intake at ad libitum meals. Weight loss in the obese has also been produced by treatment with both the serotonin precursor 5-hydroxytryptophan and the preferential 5-HT2C receptor agonist mCPP.A new generation of 5-HT2C receptor selective agonists have been developed and at least one, lorcaserin (APD356), is currently undergoing clinical trials. In addition, 5-HT6 receptor antagonists such as PRX-07034 and BVT74316 have been shown to potently reduce food intake and bodyweight gain in rodent models and have recently entered clinical trials. However, the role of the 5-HT6 receptor in the expression of appetite remains to be determined. The hope is that these drugs will not only be free of their predecessors' adverse effect profiles, but will also be equally or more effective at regulating appetite and controlling bodyweight.     

Novel actions of inverse agonists on 5-HT2C receptor systems

In cell systems where ligand-independent receptor activity is optimized (such as when receptors are overexpressed or mutated), acute treatment with inverse agonists reduces basal effector activity whereas prolonged exposure leads to sensitization of receptor systems and receptor up-regulation. Few studies, however, have reported effects of inverse agonists in systems where nonmutated receptors are expressed at relatively low density. Here, we investigated the effects of inverse agonists at human serotonin (5-HT)2C receptors expressed stably in Chinese hamster ovary cells ( approximately 250 fmol/mg protein). In these cells, there is no receptor reserve for 5-HT and 5-HT2C inverse agonists did not reduce basal inositol phosphate (IP) accumulation nor arachidonic acid (AA) release but behaved as simple competitive antagonists, suggesting that these receptors are not overexpressed. Prolonged treatment (24 h) with inverse agonists enhanced selectively 5-HT2C-mediated IP accumulation but not AA release. The enhancing effect occurred within 4 h of treatment, reversed within 3 to 4 h (after 24-h treatment), and could be blocked with neutral antagonists or weak positive agonists. The enhanced responsiveness was not due to receptor up-regulation but may involve changes in the expression of the G protein, Galphaq/11 and possibly Galpha12 and Galpha13. Interestingly, 24-h exposure to inverse agonists acting at 5-HT2C receptors also selectively enhanced IP accumulation, but not AA release, elicited by activation of endogenous purinergic receptors. These data suggest that actions of inverse agonists may be mediated through effects on receptor systems that are not direct targets for these drugs.     

Cloning, expression, and functional analysis of human dopamine D1 receptors

AIM: To construct an HEK293 cell line stably expressing human dopamine D1 receptor (D1R). METHODS: cDNA was amplified by RT-PCR using total RNA from human embryo brain tissue as the template. The PCR products were subcloned into the plasmid pcDNA3 and cloned into the plasmid pcDNA3.1. The cloned D1R cDNA was sequenced and stably expressed in HEK293 cells. Expression of D1R in HEK293 cells was monitored by the [3H]SCH23390 binding assay. The function of D1R was studied by the cAMP accumulation assay, CRE-SEAP reporter gene activity assay, and intracellular calcium assay. RESULTS: An HEK293 cell line stably expressing human D1R was obtained. A saturation radioligand binding experiment with [3H]SCH23390 demonstrated that the Kd and Bmax values were 1.5+/-0.2 nmol/L and 2.94+/-0.15 nmol/g of protein, respectively. In the [3H]SCH23390 competition assay, D1R agonist SKF38393 displaced [3H]SCH23390 with an IC50 value of 2.0 (1.5-2.8) micromol/L. SKF38393 increased the intracellular cAMP level and CRE-SEAP activity through D1R expressed in HEK293 cells in a concentration-dependent manner with an EC50 value of 0.25 (0.12-0.53) micromol/L and 0.39 (0.27-0.57) micromol/L at 6 h/0.59 (0.22-1.58) micromol/L at 12 h, respectively. SKF38393 also increased the intracellular calcium level in a concentration-dependent manner with EC50 value of 27 (8.6-70) nmol/L. CONCLUSION: An HEK293 cell line stably expressing human D1R was obtained successfully. The study also demonstrated that the CRE-SEAP activity assay could be substituted for the cAMP accumulation assay for measuring increase in cAMP levels. Thus, both intracellular calcium measurements and the CRE-SEAP activity assay are suitable for high-throughput screening in drug research.