In-cell Western法测定人胰岛素生物学活性

目的:利用in-cell Western(ICW)技术研究基于转基因细胞的人胰岛素生物学活性测定方法。方法:以CHO-INSR B1284为靶细胞，用不同浓度的人胰岛素刺激靶细胞，采用ICW技术检测人胰岛素受体酪氨酸磷酸化水平，进行人胰岛素的体外生物学活性测定；根据《中华人民共和国药典》2020年版通则9401“生物制品生物活性/效价测定方法”对该方法进行专属性、相对准确度、中间精密度、线性与范围等方法学验证；以重组人胰岛素国家标准品为参比品，采用本方法测定人胰岛素原料药及其他人胰岛素类似物的生物学活性相对效价。结果:不同浓度的人胰岛素作用于CHO-INSR B1284细胞后具有较好的剂量依赖性；5个效价浓度的待测品经8次测定，相对效价的几何均值分别为：(63.76±4.38)%,(78.01±5.97)%,(99.52±4.62)%,(122.84±7.4)%,(151.71±8.81)%,相对偏倚均在±5%范围内，对应的几何变异系数(GCV,%)均<11%,GCV的置信上限均<20%;采用该方法能有效检测人胰岛素及其胰岛素类似物的效价。结论:利用ICW技术的人胰岛素体外...     

美洛昔康片的人体药物动力学及生物利用度

目的 :研究美洛昔康片的药物动力学及相对生物利用度。方法 :采用随机交叉试验设计 ,2 0名男性健康志愿者单剂量口服试验品与参比品 15mg ,以HPLC法测定血药浓度。结果 :试验品和参比品的AUC0→t分别为 (5 2 85± 12 18) ,(5 7 10±15 5 5 )h·μg·mL-1;AUC0→∞ 分别为 (5 7 90± 14 0 3) ,(6 3 98± 19 94)h·μg·mL-1;cmax分别为 (1 493± 0 338) ,(1 6 82± 0 399) μg·mL-1;tmax分别为 (5 6 5± 3 17) ,(4 6 0± 1 82 )h ;T1/ 2 分别为 (2 6 2 9± 4 37) ,(2 8 0 3± 6 75 )h。 2种美洛昔康片的主要动力学参数 :AUC0→t,AUC0→∞ ,cmax,tmax和T1/ 2 经方差分析显示均无统计学差异 (P >0 0 5 )。AUC经双单侧t检验证明 ,试验品与参比品生物等效 ,试验品的相对生物利用度为 (94 46± 14 6 0 ) % (n =2 0 )。结论 :2种药品具有生物等效性     

阿奇霉素胶囊及片剂的生物等效性研究

目的:研究阿奇霉素胶囊及片剂在正常人体内的相对生物利用度和生物等效性。方法:采用3×3拉丁方试验设计,将24名男性健康志愿受试者随机分为3组,分别单次口服1 g阿奇霉素供试制剂与参比制剂。采用HPLC法测定阿奇霉素血药浓度。用DAS药动学程序处理试验数据,并对试验结果进行方差分析和双单侧t检验。结果:阿奇霉素胶囊及片剂供试品和参比品的药时曲线下面积(AUC_(0→T))分别为:(23.27±4.52)μg·h·ml~(-1),(23.33±5.76)μg·h·ml~(-1),(23.31±7.70)μg·h·ml~(-1);AUC_(0→∞)分别是(31.25±5.13)μg·h·ml~(-1),(30.59±6.54)μg·h·ml~(-1),(29.78±8.15)μg·h·ml~(-1);达峰时间(t_(max))分别为:(2.17±0.38)h,(2.03±0.55)h,(2.21±0.48)h;达峰浓度(C_(max))分别为:(1.260±0.109)μg·ml~(-1),(1.310±0.138)μg·ml~(-1),(1.298±0.087)μg·ml~(-1)。阿奇霉素胶囊及片剂的相对生物利...     

抗白介素-13单克隆抗体生物学活性测定方法的建立

目的:建立抗白介素-13单克隆抗体(抗IL-13单抗)的生物学活性检测方法。方法:利用L-BEAS-2B细胞系,通过荧光素酶检测系统进行抗IL-13单抗的生物学活性检测,通过抗IL-13单抗参比品与样品对比以平行线分析的方法计算样品相对百分效价,并对该方法的精密性和准确性进行验证。结果:抗IL-13单抗在该方法中存在量效关系,在半对数坐标纸上呈平行的直线分布。6批抗IL-13单抗样品经3次测定,相对百分效价平均值在(91.10±1.10)%~(105.27±7.17)%之间,RSD均小于12%;1批样品经9次测定平均相对百分效价为(110.77±7.01)%,板间和日间RSD均小于7%;2批回收率样品经3次测定,回收率分别为(96.17±8.50)%和(91.53±15.46)%。结论:研究建立的抗IL-13单抗生物学活性检测方法准确性高,精密度及重复性好,可作为抗IL-13单抗生物学活性的常规检测方法。     

阿奇霉素胶囊及片剂的人体相对生物利用度研究

目的研究阿奇霉素胶囊及片剂在正常人体内的药动学及相对生物利用度。方法采用3×3拉丁方试验设计,将24名男性健康志愿受试者随机分为3组,分别单次口服阿奇霉素供试制剂与参比制剂。采用HPLC法测定经时血药浓度。用DAS药动学程序处理试验数据,并对试验结果进行方差分析和双单侧t检验。结果阿奇霉素胶囊及片剂的相对生物利用度为:104.1%±10.2%和99.9%±9.8%;阿奇霉素胶囊及片剂供试品和参比品的药时曲线下面积(AUC0→T)分别为:23.27±4.52μg·h·ml-1、23.33±5.76μg·h·ml-1、23.31±7.70μg·h·ml-1;AUC0→∞分别是31.25±5.13μg·h·ml-1、30.59±6.54μg·h·ml-1、29.78±8.15μg·h·ml-1;达峰时间(Tmax)分别为:2.17±0.38h、2.03±0.55h、2.21±0.48h;达峰浓度(Cmax)分别是:1.260±0.109μg·ml-1、1.310±0.138μg·ml-1、1.298±0.087μg·ml-1。结论经统计学分析,制剂间药动学参数差异无显著性意义,阿奇霉素胶囊及片剂与参比制剂具有生物等效性。     

抗人SIRPα抗体制备及抗肿瘤活性研究

目的:制备抗人信号调节蛋白α(signal regulatory protein alpha, SIRPα)抗体并进行抗肿瘤活性评价。方法:通过杂交瘤技术获得高亲和力鼠抗人SIRPα抗体。采用高效液相色谱(high performance liquid chromatography, HPLC)和毛细管凝胶电泳检测抗体纯度；采用酶联免疫吸附法(enzyme linked immunosorbent assay, ELISA)及荧光激活细胞分选法(fluorescence activated cell sorting, FACS)检测抗体抗原结合活性及抗体依赖性细胞介导的吞噬(antibody-dependent cell-mediated phagocytosis, ADCP)活性；采用生物干涉膜技术(bio-layer interferometry, BLI)检测嵌合抗体与人SIRPα结合动力学；利用转基因Balb/c小鼠皮下移植CT26-hCD47/hPD-L1肿瘤细胞的模型进行候选抗体药效学评价。结果:制备出纯度高于90%的3种抗体14C4、59G5及4C10。3种抗体都能特异性...     

阿酚咖片中对乙酰氨基酸和咖啡因的相对生物利用度及其生物等效性

目的研究阿酚咖(AFC)片中的对乙酰氨基酚、咖啡因的相对生物利用度。方法采用RP-HPLC测定24名志愿受试者单剂量口服AFC片供试品与参比制剂后,血液中对乙酰氨基酚、咖啡因的变化。结果对乙酰氨基酚的相对生物利用度为100.72%±11.33%;供试品与对照品的AUC0→T分别为12.86±3.20、12.92±3.56μg.h.ml-1;Tmax分别为1.1±0.4、1.1±0.4 h;Cmax分别为3.25±0.57、3.31±0.61μg.ml-1。咖啡因的相对生物利用度为101.96%±13.65%;供试品与对照品的AUC0→T分别为10.61±1.50、10.32±1.80μg.h.ml-1;Tmax分别为1.0±0.4、1.0±0.3 h;Cmax分别是1.74±0.20、1.68±0.25μg.ml-1。结论两种制剂中的对乙酰氨基酚和咖啡因的AUC0→∞、AUC0→T、Tmax及Cmax经双单侧t检验,生物等效。     

人源VEGF单克隆抗体Fabμ和Fc5μ片段的制备

用胰蛋白酶将Mr为900 k的人源VEGFIgM单抗切成Fabμ和五聚的Fc片段(Fc5μ).用Sephacryl S-200对分离纯化两片段,用间接ELISA法测定IgM抗体及Fabμ片段的抗原结合活性.结果表明:按酶;IgM为1:30加入胰蛋白酶,63℃酶切30 min,可使IgM水解完全.用Sephacryl S-200纯化后,片段纯度≥90%.经ELISA间接法测定Fabtt的抗原结合活性后发现,虽与完整的五聚体IgM相比亲和力有所下降.但仍有较好的抗原结合活性,相对亲和力为4.29×108.     

阿双西林胶囊相对生物利用度研究

本实验采用反相高效液相色谱法测定10名志愿受试者单剂量口服1.5g阿双西林胶囊供试品与克菌胶囊标准参比制剂后,阿莫西林和双氯青霉素血药浓度变化情况,经3p87药代动力学程序处理,两种制剂阿莫西林药时曲线下面积分别是:50.47 ± 15.94 mg·h·L-1与48.68 ± 18.14 mg·h·L-1,达峰时间分别为:1.35 ± 0.34 h与1.25 ± 0.26 h,峰浓度分别是:17.79 ± 4.88 mg·L-1与 17.54 ± 7.88 mg·L-1.两种制剂双氯青霉素药时曲线下面积分别是:47.41 ± 13.05 mg·h·L-1与 46.39 ± 16.07 mg·h·L-1,达峰时间分别为: 1.45 ± 0.28 h与 1.45 ± 0.37h,峰浓度分别是:14.7 ± 5.13 mg·L-1与 14.1 ± 6.02 mg·L-1.以两种制剂阿莫西林与双氯青霉素药时曲线下面积、峰浓度及达峰时间为指标,双单侧t检验进行生物等效性评价,阿双西林胶囊供试品与克菌胶囊标准参比制剂为生物等效制剂(双侧P＜0.05).阿双西林胶囊供试品阿莫西林与双氯青霉素的相对生物利用度分别为:105.58 % ± 7.52 %和103.70 % ± 10.04 % .     

亚叶酸钙片的人体生物利用度及生物等效性研究

目的:研究亚叶酸钙片在健康受试者体内的相对生物利用度和生物等效性.方法:采用两制剂双周期随机交叉试验设计,18名男性健康受试者单剂量口服亚叶酸钙片或参比片剂75mg,用HPLC测定血浆亚叶酸浓度.采用3P97药动学程序进行数据处理.结果:试验片剂与参比片剂的AUC0-24h分别为(4608.68±806.72)ng·ml-1·h和(4868.73±909.83)ng·ml-1·h;Cmax分别为(484.82±72.87)ng·ml-1和(499.50±108.19)ng·ml-1;Tmax分别为(2.33±0.30)h和(2.47±0.27)h.结论:两种制剂主要药动学参数均无显著性差异.与参比片剂相比,试验片剂的相对生物利用度为(96.48±18.60)%,两者具有生物等效性.     

MORAb-003, a fully humanized monoclonal antibody against the folate receptor alpha, for the potential treatment of epithelial ovarian cancer

Morphotek Inc is developing MORAb-003, a humanized monoclonal antibody directed against folate receptor alpha, for the potential treatment of ovarian cancer. Phase II clinical trialsof MORAb-003, either alone or in combination with platinum/taxane chemotherapy, are underway in ovarian cancer patients experiencing their first disease recurrence.     

Imidacloprid, thiacloprid, and their imine derivatives up-regulate the alpha 4 beta 2 nicotinic acetylcholine receptor in M10 cells

Neonicotinoids are the most important new class of insecticides of the last decade. They act as nicotinic acetylcholine receptor (AChR) agonists. This investigation tests the hypothesis for the first time that neonicotinoid insecticides and their imine derivatives up-regulate the alpha 4 beta 2 nicotinic AChR subtype, which represents >90% of the high-affinity [(3)H]nicotine binding sites in mammalian brain. The alpha 4 beta 2 receptor stably expressed in mouse fibroblast M10 cells was assayed after 3 days' exposure to the test compound, as [(3)H]nicotine binding following immunoisolation by monoclonal antibody (mAb 299) or as [(125)I]mAb 299 labeling for cell surface receptors. We found that imidacloprid (IMI) (one of the most important insecticides) and thiacloprid (THIA) increased [(3)H]nicotine binding levels (up-regulation of the alpha 4 beta 2 AChRs) by five- to eightfold with EC50s of approximately 70,000 and 19,000 nM, respectively, compared with 760 nM for (-)-nicotine. In contrast, two imine analogs [the desnitro metabolite of IMI (DNIMI) and the descyano derivative of THIA] gave up-regulation by eightfold and EC50s of 870 and 500 nM, respectively. The potency order for up-regulation by the five aforementioned compounds was correlated with their in vitro IC50s for inhibiting [(3)H]nicotine binding (r(2) = 0.99, n = 5), indicating that binding to the alpha 4 beta 2 receptor initiates the up-regulation. A potent olefin derivative of the THIA imine up-regulated with an EC50 of 22 nM. DNIMI-induced up-regulation mainly occurred intracellularly rather than at the cell surface. These findings in alpha 4 beta 2-expressing M10 cells indicate the possibility that some neonicotinoid insecticides or their metabolites, on accidental human exposure or when used for flea control on dogs, may also up-regulate the receptor in mammals.     

Targeted drug delivery via the folate receptor

The folate receptor is a highly selective tumor marker overexpressed in greater than 90% of ovarian carcinomas. Two general strategies have been developed for the targeted delivery of drugs to folate receptor-positive tumor cells: by coupling to a monoclonal antibody against the receptor and by coupling to a high affinity ligand, folic acid. First, antibodies against the folate receptor, including their fragments and derivatives, have been evaluated for tumor imaging and immunotherapy clinically and have shown significant targeting efficacy in ovarian cancer patients. Folic acid, a high affinity ligand of the folate receptor, retains its receptor binding properties when derivatized via its gamma-carboxyl. Folate conjugation, therefore, presents an alternative method of targeting the folate receptor. This second strategy has been successfully applied in vitro for the receptor-specific delivery of protein toxins, anti-T-cell receptor antibodies, interleukin-2, chemotherapy agents, gamma-emitting radiopharmaceuticals, magnetic resonance imaging contrast agents, liposomal drug carriers, and gene transfer vectors. Low molecular weight radiopharmaceuticals based on folate conjugates showed much more favorable pharmacokinetic properties than radiolabeled antibodies and greater tumor selectivity in folate receptor-positive animal tumor models. The small size, convenient availability, simple conjugation chemistry, and presumed lack of immunogenicity of folic acid make it an ideal ligand for targeted delivery to tumors.     

The role of the amino acid residue at alpha1:189 in the binding of neuromuscular blocking agents to mouse and human muscle nicotinic acetylcholine receptors

BACKGROUND AND PURPOSE: Nicotinic acetylcholine receptors (AChRs) are valuable therapeutic targets. To exploit them fully requires rapid assays for the evaluation of potentially therapeutic ligands and improved understanding of the interaction of such ligands with their receptor binding sites. EXPERIMENTAL APPROACH: A variety of neuromuscular blocking agents (NMBAs) were tested for their ability to inhibit the binding of [(125)I]alpha-bungarotoxin to TE671 cells expressing human muscle AChRs. Association and dissociation rate constants for vecuronium inhibition of functional agonist responses were then estimated by electrophysiological studies on mouse muscle AChRs expressed in Xenopus oocytes containing either wild type or mutant alpha1 subunits. KEY RESULTS: The TE671 inhibition binding assay allowed for the rapid detection of competitive nicotinic AChR ligands and the relative IC(50) results obtained for NMBAs agreed well with clinical data. Electrophysiological studies revealed that acetylcholine EC(50) values of muscle AChRs were not substantially altered by non-conservative mutagenesis of phenylalanine at alpha1:189 and proline at alpha1:194 to serine. However the alpha1:Phe189Ser mutation did result in a 3-4 fold increase in the rate of dissociation of vecuronium from mouse muscle AChRs. CONCLUSIONS AND IMPLICATIONS: The TE671 binding assay is a useful tool for the evaluation of potential therapeutic agents. The alpha1:Phe189Ser substitution, but not alpha1:Pro194Ser, significantly increases the rate of dissociation of vecuronium from mouse muscle AChRs. In contrast, these non-conservative mutations had little effect on EC(50) values. This suggests that the AChR agonist binding site has a robust functional architecture, possibly as a result of evolutionary 'reinforcement'.     

Interaction of positive allosteric modulators with human and Drosophila recombinant GABA receptors expressed in Xenopus laevis oocytes.

1. A comparative study of the actions of structurally diverse allosteric modulators on mammalian (human alpha 3 beta 2 gamma 2L) or invertebrate (Drosophila melanogaster Rdl or a splice variant of Rdl) recombinant GABA receptors has been made using the Xenopus laevis oocyte expression system and the two electrode voltage-clamp technique. 2. Oocytes preinjected with the appropriate cRNAs responded to bath applied GABA with a concentration-dependent inward current. EC50 values of 102 +/- 18 microM; 152 +/- 10 microM and 9.8 +/- 1.7 microM were determined for human alpha 3, beta 1 gamma 2L, Rdl splice variant and the Rdl receptors respectively. 3. Pentobarbitone enhanced GABA-evoked currents mediated by either the mammalian or invertebrate receptors. Utilizing the appropriate GABA EC10, the EC50 for potentiation was estimated to be 45 +/- 1 microM, 312 +/- 8 microM and 837 +/- 25 microM for human alpha 3, beta 1 gamma 2L, Rdl splice variant and Rdl receptors respectively. Maximal enhancement (expressed relative to the current induced by the EC10 concentration of GABA where this latter response = 1) at the mammalian receptor (10.2 +/- 1 fold) was greater that at either the Rdl splice variant (5.5 +/- 1.3 fold) or Rdl (7.9 +/- 0.8 fold) receptors. 4. Pentobarbitone directly activated the human alpha 3 beta 1 gamma 2L receptor with an EC50 of 1.2 +/- 0.03 mM and had a maximal effect amounting to 3.3 +/- 0.4 fold of the response evoked by the EC10 concentration of GABA. Currents evoked by pentobarbitone were blocked by 10-30 microM picrotoxin and potentiated by 0.3 microM flunitrazepam. Pentobarbitone did not directly activate the invertebrate GABA receptors. 5. 5 alpha-Pregnan-3 alpha-ol-20-one potentiated GABA-evoked currents mediated by the human alpha 3 beta 1 gamma 2L receptor with an EC50 of 87 +/- 3 nM and a maximal enhancement of 6.7 +/- 0.8 fold of that produced by the GABA EC10 concentration. By contrast, relatively high concentrations (3-10 microM) of this steroid had only a modest effect on the Rdl receptor and its splice variant. 6. A small direct effect of 5 alpha-pregnan-3 alpha-ol-20-one (0.3-10 microM) was detected for the human alpha 3 beta 1 gamma 2L receptor (maximal effect only 0.08 +/- 0.01 times that of the GABA EC10). This response was antagonized by 30 microM picrotoxin and enhanced by flunitrazepam (0.3 microM). 5 alpha-Pregnan-3 alpha-ol-20-one did not directly activate the invertebrate GABA receptors. 7. Propofol enhanced GABA-evoked currents mediated by human alpha 3 beta 1 gamma 2L and Rdl splice variant receptors with EC50 values of 3.5 +/- 0.1 microM and 8 +/- 0.3 microM respectively. The maximal enhancement was similar at the two receptor types (human 11 +/- 1.8 fold; invertebrate 8.8 +/- 1.4 fold that of the GABA EC10). 8. Propofol directly activated the human alpha 3 beta 1 gamma 2L receptor with an EC50 of 129 +/- 10 microM, and at a maximally effective concentration, evoked a current amounting to 3.5 +/- 0.5 times that elicited by a concentration of GABA producing 10% of the maximal response. The response to propofol was blocked by 10-30 microM picrotoxin and enhanced by flunitrazepam (0.3 microM). Propofol did not directly activate the invertebrate Rdl splice variant receptor. 9. GABA-evoked currents mediated by the human alpha 3 beta 1 gamma 2L receptor were potentiated by etomidate (EC50 = 7.7 +/- 0.2 microM) and maximally enhanced to 8 +/- 0.8 fold of the response to an EC10 concentration of GABA. By contrast, the Rdl, or Rdl splice variant forms of the invertebrate GABA receptor were insensitive to the positive allosteric modulating actions of etomidate. Neither the mammalian nor the invertebrate receptors, were directly activated by etomidate. 10. delta-Hexachlorocyclohexane enhanced GABA-evoked currents with EC50 values of 3.4 +/- 0.1 microM and 3.0 +/- 0.1 microM for the human alpha 3 beta 1 gamma 2L receptor and the Rdl splice variant receptor respectively. The maximal enhancement was 4.5     

Estrogenic activity and estrogen receptor beta binding of the UV filter 3-benzylidene camphor. Comparison with 4-methylbenzylidene camphor

UV filters represent new classes of estrogenic [Environ. Health Perspect. 109 (2001) 239] or antiandrogenic [Toxicol. Sci. 74 (2003) 43] chemicals. We tested 3-benzylidene camphor (3-BC), reported as estrogenic in fish [Pharmacol. Toxicol. 91 (2002) 204], and mammalian systems in comparison to 4-methylbenzylidene camphor (4-MBC), shown to be active in rats, and analyzed binding to estrogen receptor subtypes. 3-BC and 4-MBC stimulated MCF-7 cell proliferation (EC(50): 0.68 and 3.9 microM). The uterotrophic assay of 3-BC (oral gavage) in immature rats showed unexpected potency with ED50 45.3mg/kg per day; lowest effective dose 2mg/kg per day, and maximum effect with 70% of ethinylestradiol. After comparing with literature data, we found that the oral 3-BC was considerably more potent than oral bisphenol A and almost as active as subcutaneous genistein. 3-BC and 4-MBC displaced 16alpha 125I-estradiol from porcine uterine cytosolic receptors (IC(50): 14.5 and 112 microM), and from recombinant human estrogen receptor beta (hERbeta) (IC(50): 3-BC, 11.8 microM; 4-MBC, 35.3 microM), whereas no displacement was detected at human estrogen receptor alpha (hERalpha) up to 3mM. This subtype selectivity makes the two camphor derivatives interesting model compounds. Their activity on immature rat uterus is not easily explained by ERbeta activation. It cannot be excluded that active metabolites with possibly different receptor binding characteristics are formed in vivo.     

Antigenic cross-reaction between the alpha types of human and mouse interferon

Cross-neutralization of the alpha and beta types of human and mouse interferons was tested using antibodies directed against the heterologous types of interferons. The alpha type of mouse interferon (MuIFN-alpha) prepared from L cells was found to be completely neutralizable by high-titered antibody against human alpha-type interferon (HuIFN-alpha), although the titers were much lower than those obtained in neutralization reactions with the homologous interferon. MuIFN-alpha from virus-induced lymphocytes, as well as non-glycosylated MuIFN-alpha from L cells, reacted similarly. The cross-reaction was also observed by the binding of anti-HuIFN-alpha antibody to a column of immobilized MuIFN-alpha. The binding experiment indicated that only a small fraction of the anti-HuIFN-alpha antibody population is heterologous reactive. Reciprocally, HuIFN-alpha from L cells, again with relatively low antibody titers, and the antibody responsible for the heterologous reaction was shown to be the anti-MuIFN-alpha and not anti-MuIFN-beta type. It is concluded that the alpha types of human and mouse interferon bear an antigenic homology. On the other hand, no significant antigenic cross-reactivity has been detected between the beta types of human and mouse interferons.     

Pharmacological characterization of a receptor for calcitonin gene-related peptide on rat, L6 myocytes.

1 The L6 myocyte cell line expresses high affinity receptors for calcitonin gene-related peptide (CGRP) which are coupled to activation of adenylyl cyclase. The biochemical pharmacology of these receptors has been examined by radioligand binding or adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation. 2 In intact cells at 37 degrees C, human and rat alpha- and beta-CGRP all activated adenylyl cyclase with EC50s of about 1.5 nM. A number of CGRP analogues containing up to five amino acid substitutions showed similar potencies. In membrane binding studies at 22 degrees C in 1 mM Mg2+, the above all bound to a single site with IC50s of 0.1-0.4 nM. 3 The fragment CGRP(8-37) acted as a competitive antagonist of CGRP stimulation of adenylyl cyclase with a calculated Kd of 5 nM. The Kd determined in membrane binding assays was lower (0.5 nM). 4 The N-terminal extended human alpha-CGRP analogue Tyro-CGRP activated adenylyl cyclase and inhibited [125I]-iodohistidyl-CGRP binding less potently than human alpha-CGRP (EC50 for cyclase = 12 nM, IC50 for binding = 4 nM). 5 The pharmacological profile of the L6 CGRP receptor suggests that it most closely resembles sites on skeletal muscle, cardiac myocytes and hepatocytes. The L6 cell line should be a stable homogeneous model system in which to study CGRP mechanisms and pharmacology.     

Gain of function mutation of the alpha7 nicotinic receptor: distinct pharmacology of the human alpha7V274T variant

In the human alpha7 nicotinic receptor, valine-274 in the pore-lining transmembrane-2 region was mutated to threonine to produce the variant human alpha7V274T, which was evaluated electrophysiologically following expression in Xenopus laevis oocytes. Inward current rectification was strong in human alpha7V274T as in the human alpha7 wild type nicotinic receptor. However, human alpha7V274T was 100-fold more sensitive to the nicotinic receptor agonists acetylcholine, (-)-nicotine and 1,1-dimethyl-4-phenylpiperazinium. Choline also activated human alpha7V274T (EC50 = 12 microM) and was 82-fold more potent than at human alpha7 wild type nicotinic receptor. (-)-Cotinine, (2,4)-dimethoxybenzylidene anabaseine (GTS-21) and 2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine (ABT-089), weak partial agonists at human alpha7 wild type, were much stronger agonists at human alpha7V274T with EC50 values of 70 microM, 4 microM and 28 microM and fractional activation values of 93%, 96% and 40%, respectively. However, (-)-lobeline, a human alpha7 wild type nicotinic receptor antagonist, and dihydro-beta-erythroidine, which activates chick mutagenized alpha7 nicotinic receptors, had only weak agonist-like activity at human alpha7V274T (< or = 4% of the maximal acetylcholine response). Methyllycaconitine, mecamylamine, d-tubocurarine and dihydro-beta-erythroidine retained antagonist activity and, indeed, appeared to be at least as potent at human alpha7V274T as at human alpha7 wild type. These results support and extend the concept that human nicotinic receptor pharmacology can be profoundly altered by single amino acid changes in the pore-lining segment.     

Inhibition of adenylate cyclase is mediated by the high affinity conformation of the alpha 2-adrenergic receptor

The functional significance of high affinity agonist binding to receptors that interact with guanine nucleotide regulatory proteins has remained controversial. Preincubation of human platelet membranes with the full alpha 2-agonist UK 14,304 in the absence of GTP increases the potency of the agonist to inhibit adenylate cyclase in a pre-steady state (15-sec) assay. The EC50 after preincubation (6 +/- 1 nM) is within a factor of 2 of the high affinity Kd for [3H]UK 14,304 binding determined under identical conditions (2.7 +/- 0.1 nM). In contrast, in the usual steady state measurements (15 min) or in pre-steady state measurements without agonist preincubation, the EC50 values (74 +/- 1 and 207 +/- 8 nM, respectively) are near the low affinity Kd for [3H]UK 14,304 binding. Reduction of the GTP concentration in steady state adenylate cyclase assays also decreases the EC50 for UK 14,304 from 40 +/- 5 nM at 10 microM GTP to 14 +/- 5 nM with no added GTP. Both sets of experimental observations are accommodated by a complete kinetic model of inhibition in which the high affinity ternary complex of drug, receptor, and G protein leads to the response. Explicit rate parameters are included for agonist binding, receptor-G protein interactions, GTP binding, and hydrolysis. Despite the functional role of the high affinity state of the alpha 2-receptor in this model, the steady state EC50 for agonist-mediated inhibition correlates best with the Kd of low affinity agonist binding in the presence of high levels of GTP. Under conditions in which formation of the high affinity ternary complex is favored, the EC50 for responses approaches the high affinity Kd.