葛根素和大豆甙元抑制[3H]氟硝西泮和体外大鼠脑膜的结合

从中药葛根中提取到两种苯二氮艹卓受体活性化合物:葛根素和大豆甙元。两种化合物在体外可抑制[3H]氟硝西泮和大鼠脑细胞膜的结合,IC₅₀值分别为18.46μmol·L^-1和15.43μmol·L^-1。大豆甙元还可抑制[³H]哌唑嗪和α1-肾上腺素受体的结合(IC₅₀值为89μmol·L^-1)。两种化合物的GABA比分别为1.11和1.12,提示两种黄酮化合物是苯二氮艹卓受体的拮抗剂或部分激动剂。Scatchardplot分析显示:两种化合物对[³H]氟硝西泮与膜结合的抑制作用是通过竞争性与非竞争性混合机制而实现的。     

从远志中分离鉴定出一种多巴胺受体活性化合物

从中药远志中提出一种多巴胺受体的配基,四氢非州防己胺。此化合物在体外可抑制[³H]SCH23390和[³H]螺哌隆与大鼠纹状体膜的结合,IC₅₀值分别为0.75±0.08μmol·L^-1和0.92±0.10μmol·L^-1。它在体外还能抑制[³H]哌唑嗪和大鼠脑皮质细胞膜结合(IC₅₀值为46μmol·L^-1),但不能改变[³H]QNB及[³H]muscimol对膜的结合。Scatchandplot分析显示此化合物对[³H]SCH23390和[³H]螺哌隆与膜结合的抑制作用是通过竞争性与非竞争性混合机制而实现的。     

四肽FMRFa对大鼠心室肌Na+/Ca2+交换的抑制

目的　研究四肽FMRFa对大鼠单个心室肌细胞Na⁺/Ca²⁺交换的作用。方法　用膜片钳全细胞记录法测定成年大鼠心室肌细胞Na⁺/Ca²⁺交换电流(I_Na⁺/Ca²⁺)和其他离子通道电流。结果　FMRFa对大鼠心室肌细胞I_Na⁺/Ca²⁺呈浓度依赖性抑制,100μmol·L^-1浓度时抑制内向和外向I_Na⁺/Ca²⁺密度分别达60.1%和56.5%,对内向电流及外向电流的IC₅₀分别为20μmol·L^-1和34μmol·L^-1。FMRFa5μmol·L^-1抑制I_Na⁺/Ca²⁺内向和外向电流密度分别为38.7%和34.9%,但FMRFa5μmol·L^-1及20μmol·L^-1对L型钙电流、钠电流、瞬时外向电流和内向整流钾电流均无显著抑制作用。结论　FMRFa对大鼠心室肌细胞是一个特异性Na⁺/Ca²⁺交换抑制剂。     

UPLC-MS/MS测定大鼠血浆中香附烯酮和α-香附酮浓度及其药动学研究

目的 建立UPLC-MS/MS测定大鼠血浆中香附烯酮和α-香附酮的方法，并研究其药动学。方法 采用Phenomennex C₁₈(150 mm×2.0 mm，3 μm)色谱柱，以乙腈-水为流动相进行梯度洗脱，柱温30 ℃，进样量1 μL，蛇床子素为内标，采用电喷雾离子源，正离子模式，香附烯酮m/z为219.1/135.1，α-香附酮m/z为219.1/111.0，蛇床子素m/z为245.0/123.0。检测大鼠血浆中香附烯酮、α-香附酮的浓度，应用DAS 2.0软件拟合主要的药动学参数。结果 香附烯酮在10~500 ng·mL^-1内线性关系良好(r=0.991 0)，α-香附酮在2.5~300 ng·mL^-1内线性关系良好(r=0.994 1)，日内精密度RSD＜9.45%，日间精密度RSD＜9.09%，加样回收率＞86.79%。SD大鼠灌胃给予香附挥发油提取物(20 mg·kg^-1)后，香附烯酮和α-香附酮C_max、AUC_0-∞、MRT_(0-∞)分别为(8 862.59±1 106.81)ng·L^-1，(7 060.94±774.25)ng·L^-1·h，(3.21±0.72)h和(934.69±106.81)ng·L^-1，(792.26±74.52)ng·L^-1·h，(4.94±0.82)h。结论 建立的方法能够快速、准确测定血浆中香附烯酮和α-香附酮的浓度，可用于香附烯酮和α-香附酮在大鼠体内的药动学研究。     

脑5-HT1A/1B、α2受体及腺苷酸环化酶参与了胍丁胺的抗抑郁作用

为了在单胺受体及受体后腺苷酸环化酶(adenylate cyclase,AC)水平探讨胍丁胺(agmatine,AGM)抗抑郁作用的精细机制,采用小鼠悬尾实验和强迫游泳实验观察AGM抗抑郁行为改变。采用放射免疫方法测定大鼠前额皮层突触膜蛋白AC活性。结果表明,AGM(5～40 mg·kg^-1,ig)在小鼠悬尾实验和强迫游泳实验模型上均有显著抗抑郁活性。同时伍用β受体/5-HT_1A/1B受体阻断剂吲哚洛尔(pindolol, PIN, 20 mg·kg^-1, ip)、 α₂肾上腺素受体拮抗剂育亨宾(yohimbine, YOH, 5～10 mg·kg^-1, ip)或咪唑克生(idazoxan, IDA, 4 mg·kg^-1, ip)对AGM(40 mg·kg^-1, ig)的抗抑郁活性具有显著拮抗效应; 而β受体阻断剂普萘洛尔(propranolol, PRO, 5～20 mg·kg^-1, ip)或5-HT₃受体拮抗剂曲匹西隆(tropisetron, TRO, 5～40 mg·kg^-1, ip)对AGM(40 mg·kg^-1, ig)的抗抑郁活性无显著影响。AGM(0.1～6.4 μmol·L^-1)与大鼠前额皮层提取的突触膜共孵可剂量依赖地激活AC活性, 而PIN(1 μmol·L^-1)或YOH(0.25～1 μmol·L^-1)均显著拮抗AGM(6.4 μmol·L^-1)对AC的激活作用; 慢性给予大鼠AGM(10 mg·kg^-1, ig, bid)或氟西汀(fluoxetine, FLU, 10 mg·kg^-1, ig, bid) 2 w也显著增强大鼠前额皮层基础及Gpp(NH)p 预激活的AC活性。本研究表明, 调节脑内5-HT_1A/1B和α₂等受体功能, 并激活前额皮层AC可能是AGM抗抑郁活性的重要机制之一。     

赛庚啶对大鼠心肌细胞膜［~3H］－d－cis－硫氮卓酮结合部位的影响

苯并噻嗪类钙通道阻滞剂［３Ｈ］－ｄ－ｃｉｓ－硫氮酮能以一种特异和可饱和的方式与离体大鼠心肌细胞膜结合，其ＫＤ值和Ｂｍａｘ分别为８４ｎｍｏｌ·Ｌ－１和０．２７９ｐｍｏｌ·ｍｇｐｒｏｔｅｉｎ－１。非标记的硫氮酮和赛庚啶均能完全抑制这种结合，其Ｋｉ值分别为１０２ｎｍｏｌＬ－１和５．５ｕｍｏｌ·Ｌ－１。上述结果证实在大鼠心肌细胞膜上也存有［３Ｈ］－硫氮酮受体，同时还提示赛马庚啶对心肌细胞膜的钙通道阻滞作用可能与作用于心肌细胞膜［３Ｈ］硫氮酮受体有关。     

4-氨基吡啶对豚鼠心室肌钙和钠电流的影响

目的研究4-氨基吡啶(4-AP)对心肌细胞L型钙通道和钠通道的影响。方法用全细胞膜片钳技术考察4-AP对豚鼠心室肌细胞L型钙电流和钠电流的作用。结果4-AP0.1,0.5,1.0mmol·L^-1浓度依赖性地抑制L型钙电流(I_Ca,L)和钠电流(I_Na),抑制率分别为(11.6±1.7)%,(37.5±8.3)%和(54.5±6.9)%以及(22.1±14.3)%,(39.4±8.8)%和(62.3±6.8)%。0.5mmol·L^-14-AP使I_Ca,L和I_NaI-V曲线均上移。结论4-AP可浓度依赖性地阻滞豚鼠心室肌细胞L型钙通道和钠通道。     

丁基苯酞对原代培养的大鼠皮层神经细胞外液6-keto-PGF1α和TXB2及其比值的影响

目的旨在观察丁基苯酞(NBP)对神经细胞培养液中6-酮-PGF_1α和TXB₂含量及其比值的影响。用放射免疫方法,结果发现神经细胞在低糖低氧5h或低糖低氧5h/恢复糖氧3h条件下,d-,l-和dl-NBP(0.1～100μmol·L^-1)能够剂量依赖性升高细胞外液中的6-酮-PGF_1α含量,降低TXB₂水平,从而使6-酮-PGF_1α与TXB₂比值升高。而阿司匹林仅在小剂量(0.1,1μmol·L^-1)时能升高6-酮 PGF^1α与TXB^{2比值,大剂量(10,100μmol·L-1)时无影响。提示:NBP对6-酮-PGF_1α/TXB₂比值的升高可能与其增加局部脑血流和改善缺血性脑损伤有关。}     

AMP579与腺苷对大鼠和豚鼠心室肌钾离子或钠离子通道作用的比较

目的研究AMP579和腺苷对钾离子与钠离子通道的影响及其作用机制，比较它们对负性变力及抗心律失常作用的离子机制。方法采用膜片钳全细胞记录模式记录大鼠和豚鼠心室肌细胞离子通道电流。结果腺苷对大鼠心室肌瞬时外向钾电流(I_{to)的激动作用强于AMP579，腺苷和AMP579的EC50值分别为2.33与8.32 μmol·L^-1 (P<0.05)；两者激动Ito的作用均可被腺苷A1受体阻滞剂PD116948阻断，表明其作用机制均是通过腺苷A1受体介导的。腺苷对豚鼠心室肌延迟整流钾电流(IK)的抑制作用强于AMP579，腺苷和AMP579的IC50值分别为1.21与2.31 μmol·L^-1 (P<0.05)；AMP579对内向整流钾电流(IK1)的抑制作用强于腺苷，AMP579和腺苷的IC50值分别为4.15与20.7 μmol·L^-1 (P<0.01)。AMP579和腺苷对大鼠心室肌钠电流(INa)的抑制作用相似，其IC50值分别为9.46与6.23 μmol·L^-1。结论腺苷对大鼠心室肌Ito的激动作用强于AMP579，两者对Ito的作用机制均是通过腺苷A1受体介导的。AMP579对IK1的抑制作用强于腺苷，而腺苷对IK的抑制作用强于AMP579，两者对INa的抑制作用相似，这些离子机制与两者发挥负性变力与抗心律失常作用有关系。}     

溴泰君(W198)在大鼠和比格狗体内的药代动力学

目的研究溴泰君(W198)在大鼠和比格狗的药代动力学。方法采用HPLC紫外检测方法测定大鼠及比格狗注射W198后血清药物浓度。结果大鼠iv W198 10,20和40 mg·kg^-1 3个剂量的T_1/2β分别为6.60,7.36和6.77 h,AUC_0-24h分别为3.797,7.371和15.192 mg·h·L^-1,V_d分别为7.14,4.33和4.13 L·kg^-1,CL分别为2.83,2.60和2.71 L·(kg·h)^-1。大鼠im W198 20 mg·kg^-1后T_1/2β为11.61 h,AUC_0-24h为4.191 mg·h·L^-1,im的生物利用度为56.9%。比格狗iv W198 5 mg·kg^-1,T_1/2β为11.72 h,AUC_0-24h为12.646 mg·h·L^-1,V_d为0.70 L·kg^-1,CL为0.46 L·(kg·h)^-1。W198与人血浆蛋白的结合率平均为78.0%。结论W198 im的T_1/2β比iv的略长,其生物利用度为56.9%。在10～40 mg·kg^-1剂量内的吸收呈现一级动力学特征。     

[3H]HOE166 defines a novel calcium antagonist drug receptor — distinct from the 1,4 dihydropyridine binding domain

Summary Benzothiazinones represent a novel class of drugs which block voltage-dependent L-type calcium channels in different tissues. [³H]HOE166 (R-(±)-3,4-dihydro-2-isopro-opyl-4-methyl-2-[2-[4-[4-[2-(3, 4, 5-trimethoxyphenyl)ethyl]piperazinyl]butoxy]phenyl]-2H -1, 4-benzothiazin-3-on-dihydrochloride; 57 Ci/mmol) a potent optically pure benzothiazinone was employed to characterize receptors associated with skeletal muscle transverse tubule calcium channels. [³H]HOE166 reversibly labels the membrane-bound calcium channels with high affinity (K_d = 0.36 ± 0.05 nM; B_max = 18.2 ± 3.3 pmol/mg of membrane protein; means ± SD, n = 13), HOE166 (K_i = 0.76 nM) is 29-fold more potent than the respective (S)-enantiomer (K_i = 22.1 nM). Binding is inhibited by divalent and trivalent cations (Cd²⁺ and La³⁺ being most potent) and other calcium channel drugs (1,4 dihydropyridines, phenylalkylamines, benzothiazepines). High affinity [³H]HOE166 binding activity is maintained (Kd = 4.5–9.0 nM) after solubilization and purification (554–1350 pmoles/mg of protein) of the calcium channel complex from transverse-tubule membranes. The following data support our recent claim (Striessnig et al. 1985, 1988) that HOE166 labels a domain on L-type calcium channels which is distinct from that defined by 1,4 dihydropyridines, phenylalkylamines or benzothiazepines: (1) All 1,4 dihydropyridine-, phenylalkylamine-and benzothiazepine-receptor-selective drugs tested are only very weak inhibitors of [³H]HOE166 binding. (2) (+)-PN200-110 only partially inhibits [³H]HOE166 binding to the purified calcium. channel complex. (3) The decay of the [³H]HOE166-receptor complex is monoexponential but the dissociation rate constants depend on the ligand concentration; (+)-PN200-100 accelerates the dissociation in the presence of unlabelled HOE166. (4) Nanomolar concentrations of HOE166 and HOE167 completely inhibit (–)-[³H]desmethoxyverapamil binding to a Drosophila phenylalkylamine receptor (which lacks a 1,4 dihydropyridine binding domain). Taken together, these results are incompatible with the view that [³H]HOE166 binds competitively to the calcium channel linked 1,4 dihydropyridine drug receptors.Abbreviations kd dissociation constant - K_i inhibition constant - k_–1,k₊₁ dissociation, association rate constant - SDS sodium dodecyl sulfate - T-tubule transverse tubule - s_20,w sedimentation coefficient Send offprint requests to H. Glossmann at the above address     

Calcium Antagonism and Structure-affinity Relationships of Terfenadine,a Histamine H1 Antagonist,and Some Related Compounds

Abstract— Calcium channel affinity of terfenadine and its optical isomers was determined by the displacement of [³H]nitrendipine on rat cerebral cortex membranes. Terfenadine showed a pK_d of 6·36±0·03 whereas its R(+)-isomer (VUF4567) had a pK_d value of 6·39±0·03 and the S(–)-isomer (VUF4568) had a pK_d of 6·40 ± 0·04. The same affinity between the enantiomers suggests that the binding domain on the membrane is not sterically restricted towards the part of the molecule in which the chiral centre is present. The characteristics of terfenadine in regulating [³H]nitrendipine binding were similar to those of some other diphenyl-alkylamine type calcium antagonists. It allosterically altered the binding affinity for nitrendipine and acted at the same site linked to the calcium channel as gallopamil. A structure-affinity relationship among a group of terfenadine analogues is discussed.     

Binding of [H]MSX-2 (3-(3-hydroxypropyl)-7-methyl-8-(m-methoxystyryl)-1-propargylxanthine) to rat striatal membranes — a new, selective antagonist radioligand for A2A adenosine receptors

The present study describes the preparation and binding properties of a new, potent, and selective A_2A adenosine receptor (AR) antagonist radioligand, [³H]3-(3-hydroxypropyl)-7-methyl-8-(m-methoxystyryl)-1-propargylxanthine ([³H]MSX-2). [³H]MSX-2 binding to rat striatal membranes was saturable and reversible. Saturation experiments showed that [³H]MSX-2 labeled a single class of binding sites with high affinity (K_d=8.0 nM) and limited capacity (B_max=1.16 fmol·mg⁻¹ of protein). The presence of 100 μM GTP, or 10 mM magnesium chloride, respectively, had no effect on [³H]MSX-2 binding. AR agonists competed with the binding of 1 nM [³H]MSX-2 with the following order of potency: 5′-N-ethylcarboxamidoadenosine (NECA)>2-[4-(carboxyethyl)phenylethylamino]-5′-N-ethylcarboxamidoadenosine (CGS-21680)>2-chloroadenosine (2-CADO)>N⁶-cyclopentyladenosine (CPA). AR antagonists showed the following order of potency: 8-(m-bromostyryl)-3,7-dimethyl-1-propargylxanthine (BS-DMPX)>1,3-dipropyl-8-cyclopentylxanthine (DPCPX)>(R)-5,6-dimethyl-7-(1-phenylethyl)-2-(4-pyridyl)-7H-pyrrolo[2,3-d]pyrimidine-4-amine (SH-128)>3,7-dimethyl-1-propargylxanthine (DMPX)>caffeine. The K_i values for antagonists were in accordance with data from binding studies with the agonist radioligand [³H]CGS21680, while agonist affinities were 3–7-fold lower. [³H]MSX-2 is a highly selective A_2A AR antagonist radioligand exhibiting a selectivity of at least two orders of magnitude versus all other AR subtypes. The new radioligand shows high specific radioactivity (85 Ci/mmol, 3150 GBq/mmol) and acceptable nonspecific binding at rat striatal membranes of 20–30%, at 1 nM.     

Effect of bay K 8644, a calcium channel agonist,on dog cardiac muscarinic receptors

To investigate further whether the effects of the dihydropyridine (DHP) drugs on calcium channels are related to those of these drugs on muscarinic receptors, the binding characteristics of the DHP calcium channel agonist, Bay K 8644, on muscarinic receptors and calcium channels were compared to those of the DHP calcium channel antagonists, nicardipine and nimodipine in the dog cardiac sarcolemma. Bay K 8644, nicardipine and nimodipine inhibited the specific [³H]QNB binding with K _i values of 16.7μM, 3.5μM and 15.5μM respectively. Saturation data of [³H]QNB binding in the presence of these DHP drugs showed this inhibition to be competitive. Bay K 8644, like nicardipine and nimodipine, blocked the binding of [³H]nitrendipine to the high affinity DHP binding sites, but atropine did not, indicating that the muscarinic receptors and the DHP binding sites on calcium channels are distinct. The K _i value of Bay K 8644 for the DHP binding sites was 4 nM. Nicardipine and nimodipine (K _i :0.1–0.2 nM) were at least 20 times more potent than Bay K 8644 in inhibiting [³H]nitrendipine binding. Thus, the muscarinic receptors were about 4000 times less sensitive than these high affinity DHP binding sites to Bay K 8644. These results suggest that the DHP calcium agonist Bay K 8644 binds directly to the muscarinic receptors but its interaction with the muscarinic receptors is not related to its binding to the DHP binding sites on calcium channels.     

CHARACTERIZATION OF BINDING SITES FOR [3H]-IDAZOXAN, [3H]-P-AMINOCLONIDINE AND [3H]-RAUWOLSCINE IN THE KIDNEY OF THE DOG

1. We characterized the binding of [³H]-rauwolscine, [³H]-p-aminoclonidine and [³H]-idazoxan in a dog kidney membrane preparation. Our aim was to determine the pharmacological nature of the α₂-adrenoceptor- and imidazoline-preferring binding sites in this organ. 2. [³H]-Rauwolscine bound to an apparent single site with an affinity (K_D) of 2.2 nmol/ L and a maximum density (B_max) of 58.5 fmol/mg protein, when 10 μmol/L idazoxan defined non-specific binding. However displacement studies demonstrated that a number of compounds, including prazosin, inhibited [³H]-rauwolscine binding in a complex manner consistent with displacement from two distinct binding sites. The majority (69%) of the [³H]-rauwolscine binding sites had a relatively low affinity for prazosin (K_I= 398 nmol/L), while the remainder had a relatively high affinity for prazosin (K_I= 7.9 nmol/ L). 3. [³H]-p-Aminoclonidine bound to an apparent single site (K_D= 5.2 nmol/L; B_max= 72.4 fmol/mg protein), when 10 μmol/L phentolamine defined non-specific binding. When 1 μmol/L of the potent and selective α₂-adrenoceptor antagonist 2-methoxyidazoxan was included in the incubate, no specific binding was detected. We therefore conclude that under the conditions of this experiment [³H]-p-aminoclonidine binds only to α₂-adrenoceptors in the dog kidney. 4. [³H]-Idazoxan bound to two sites, with a higher (K_D= 0.95 nmol/L; B_max= 43.9 fmol/mg protein) and lower (K_D= 9.1 nmol/L; B_max= 93.8 fmol/mg protein) affinity, respectively, when 1 mmol/L phentolamine defined non-specific binding. When 10 μmol/ L GTPγS was included in the incubate, the low affinity site was unaffected but the maximum binding at the higher affinity site was reduced by 79%. 2-Methoxyidazoxan displaced [³H]-idazoxan in a monophasic manner and with low potency (IG₅₀=11.5 μmol/L). Yohimbine, efaroxan, clonidine, rilmenidine, guanabenz and idazoxan itself displaced [³H]-idazoxan in a complex manner; the slope of the displacement curves being less than unity. 5. We conclude that the dog kidney contains a heterogeneous population of α₂-adrenoceptors that can be labelled either with [³H]-rauwolscine or [³H]-p-aminoclonidine. The dog kidney also contains a heterogeneous population of non-adrenoceptor imidazoline-preferring binding sites of the I₂-subtype, that can be labelled with [³H]-idazoxan. The binding site for which [³H]-idazoxan has the highest affinity appears to be coupled to a guanine nucleotide binding regulatory protein.     

A1-and A2-PURINOCEPTORS IN THE GUINEA-PIG UTERUS

1. Radioligand binding and functional studies were undertaken to investigate the P₁-purinoceptors present in the separated myometrial layers and the endometrium of the guinea-pig uterus. 2. In preparations of endometrium-denuded circular myometrium, the A₂-selective agonists (2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamido-adenosine (CGS 21680, 100 μmol/L) and N-ethylcarboxamido adenosine (NECA, 1–10 μmol/L) inhibited contractile responses to phenylephrine. In preparations of endometrium-intact circular myometrium, NECA (10 μmol/L) enhanced responses to phenylephrine. NECA did not modulate the spontaneous contractions of longitudinal myometrium. 3. Homogenate binding studies with circular myometrium, longitudinal myometrium and endometrium revealed saturable high affinity [³H]-NECA binding sites. The mean maximal densities of binding sites (B_max) were 2.08, 14.7 and 15.5 fmol/mg protein, and pK_D (neg. log dissociation constant) values were 9.82, 9.19 and 7.44, respectively. 4. (R-) and (S-) -N⁶-(2-phenylisopropyl)adenosine (R- and S-PIA) both competed for two [³H]-NECA binding sites in preparations of circular myometrium. CGS 21680 competed for two [³H]-NECA binding sites in preparations of endometrium and longitudinal myometrium. All other agonist competition was for one site only. The rank orders of potency of high affinity binding were S-PIA ≥ R-PIA ≥ CGS 21680 (circular myometrium), R-PIA ≥ CGS 21680 ≥ S-PIA (longitudinal myometrium) and CGS 21680 > > S-PIA ≥ R-PIA (endometrium). 5. In preparations of circular myometrium, longitudinal myometrium and endometrium the selective A₁-purinoceptor antagonist, 1,3-dipropyl-8-(2-amino-4-chloro)-phenylxanthine (PACPX), competed for two [³H]-NECA binding sites, the non-selective antagonist 3,7-dimethyl-1-propargylxanthine (DMPX), competed for one site only. 6. NECA increased cyclic adenosine monophosphate (CAMP) levels in preparations of both circular myometrium and endometrium. 7. These results indicate that P₁-purinoceptors of the A₂-subtype mediate the inhibitory effects of adenosine analogues on the phenylephrine-induced contractions of the circular myometrium of the guinea-pig, this effect is modified by the presence of the endometrium. There is no evidence that the [³H]-NECA binding sites of the longitudinal myometrium correlate with functional P₁-purinoceptors in this tissue.     

Neurotoxic aminoglycoside antibiotics are potent inhibitors of [125I]-Omega-Conotoxin GVIA binding to guinea-pig cerebral cortex membranes

Summary [¹²⁵I]-Omega-Conotoxin GVIA, a blocker of neuronal (N-type) calcium channels labelled 295 ± 121 fmol per mg protein of high affinity sites (apparent half-saturation at 1.5 to 2.5 pmol/1) in guinea-pig cerebral cortex membranes.Divalentcations (Cd²⁺ > Ni²⁺ > Co²⁺ > Ca²⁺ > Sr²⁺ = Ba²⁺ > Mg²⁺) and La³⁺ were potent inhibitors of Omega-Conotoxin GVIA binding, whereas monovalent cations (Na⁺, K⁺, Li⁺) were ineffective up to 50 mmol/1. Aminoglycosides (neomycin > gentamycin = tobramycin > streptomycin > amikacin > kanamycin) and polymyxin B also inhibited [¹²⁵¹I]-Omega-Conotoxin GVIA binding with IC₅₀ values in the molar range. All other antibiotics tested were ineffective up to 1 mmol/1. With the exception of polymyxin B, which partially inhibited the binding of the 1,4-dihydropyridine (+)-[³H]PN 200–110 and of (–)-[³H]desmethoxyverapamil, the aminoglycosides and the other antibiotics had no effect on the L-type calcium channel labelling. It is suggested, that inhibition of neurotransmitter release by aminoglycosides is mediated via blockade of the N-type calcium channel to which [¹²⁵I]-Omega-Conotoxin GVIA binds selectively in a quasi irreversible manner.Abbreviations B _max maximum capacity of binding sites - MTL maximum therapeutic level Send offprint requests to H. Glossmann     

Evidence for multiple receptor sites within the putative calcium channel

Summary [³H]-Nimodipine, a potent calcium channel blocker, binds to an apparently homogeneous population of receptors in guinea-pig brain membranes (K_D=0.62 nM, Hill coefficient}1.0). Diltiazem (10^–5 M) lowers the K_D for [³H]-nimodipine by a factor of 3 without changing the maximum number of binding sites. Diltiazem decreased the dissociation rate constant of the nimodipine-receptor complex from 0.18 min^–1 to 0.049 min^–1 and altered the pharmacological profile as revealed by displacement studies with (–) and (+) verapamil, (–) and (+) prenylamine and 1,4 dihydropyridines. In conclusion [³H]-nimodipine binding can be utilized as a tool to evaluate complex molecular interactions between calcium channel blockers.     

间硝苯地平对血管紧张素Ⅱ促进血管平滑肌细胞增殖和蛋白质合成的影响

以培养血管平滑肌细胞(vascularsmcothmusclecell,VSMC)为模型,观察了间硝苯地平(m-nifedipine,m-Nif)对血管紧张素Ⅱ(angiotensinⅡ,ANGⅡ)促进VSMC增殖和蛋白质合成的影响。结果表明,m-Nif抑制ANGⅡ(100nmol·L^-1)引起VSMC[³H]thymidine和[³H]leucine参入,并呈剂量依赖性。m-Nif(2×10^-6mol·L^-1)可抑制ANGⅡ对VSMC的刺激、DNA及蛋白质合成速率,分别降低了46%,58%,53%。提示m-Nif可抑制ANGⅡ对VSMC增殖和蛋白合成的促进作用。