Amlodipine inhibits thapsigargin-sensitive CA(2+) stores in thrombin-stimulated vascular smooth muscle cells

Ca(2+) channel blockers, such as amlodipine, inhibit vascular smooth muscle cell (VSMC) growth through interactions with targets other than L-type Ca(2+) channels. The effects of amlodipine on Ca(2+) movements in thrombin- and thapsigargin-stimulated VSMCs were therefore investigated by determining the variations of intracellular free Ca(2+) concentration in fura 2-loaded cultured VSMCs. Results indicated that 10-1,000 nM amlodipine inhibited 1) thrombin-induced Ca(2+) mobilization from a thapsigargin-sensitive pool and 2) thapsigargin-induced Ca(2+) responses, including Ca(2+) mobilization from internal stores and store-operated Ca(2+) entry. These effects of amlodipine do not involve L-type Ca(2+) channels and could not be reproduced with 100 nM isradipine, diltiazem, or verapamil. The inhibition by amlodipine of Ca(2+) mobilization appears therefore to be a specific property of the drug, in addition to its Ca(2+) channel-blocking property. It is suggested that amlodipine acts in this capacity by interacting with Ca(2+)-ATPases of the sarcoplasmic reticulum, thus modulating the enzyme activity. This mechanism might participate in the inhibitory effect of amlodipine on VSMC growth.     

The combination of atenolol and amlodipine is better than their monotherapy for preventing end‐organ damage in different types of hypertension in rats

Combinations therapy is often used in hypertensive patients whether combination therapy is necessary for preventing end‐organ damage is not known. The objective of this study was to determine in four different hypertensive animal models the necessity of adding the calcium channel blocker amlodipine to therapy with the ß‐blocker atenolol to modulate end‐organ damage. Spontaneously hypertensive rats, DOCA‐salt hypertensive rats, two‐kidney, one‐clip renovascular hypertensive rats and Lyon genetically hypertensive rats were used to study this objective. These animal models have different sensitivities to atenolol and amlodipine. The dosages of therapy employed were 10 mg/kg atenolol alone, 1 mg/kg amlodipine, 10 mg atenolol + 1 mg/kg amlodipine and 5 mg/kg atenolol+0.5 mg/kg amlodipine. BP was continuously recorded in all animals. After determination of baroreflex sensitivity, rats were sacrificed for end‐organ damage evaluation. The combination of amlodipine and atenolol had a synergistic inhibitory effect on blood pressure and blood pressure variability, and end‐organ damage as compared with monotherapy with atenolol or amlodipine in all animal models. Baroreflex sensitivity also improved with the combination therapy more than with monotherapy. In conclusion, atenolol and amlodipine combination exerts a superior effect on blood pressure, blood pressure variability, baroreflex sensitivity and end‐organ damage. The superior effect of the combination was observed in all four models of hypertension.     

Automated gas chromatographic assay for amlodipine in plasma and gingival crevicular fluid

This paper describes an automated capillary gas chromatographic method for the determination of amlodipine in plasma, and in sub-microlitre volumes of gingival crevicular fluid (GCF), in order to assess if amlodipine is present in GCF under conditions of gingival overgrowth, as has been shown for nifedipine, another dihydropyridine drug. Liquid-liquid extraction followed by derivatisation was employed to isolate amlodipine and render it suitable for gas chromatography. Amlodipine was analysed in plasma and GCF of four patients undergoing amlodipine therapy for cardiovascular disorders, three of whom had significant gingival overgrowth. Amlodipine was detected in the plasma of all patients and in massive concentrations in the GCG of those patients with overgrowth, 23- to 290-fold greater than in their plasma. Like nifedipine, amlodipine sequestration into GCF appears to be linked with gingival overgrowth.     

Novel anti-inflammatory actions of amlodipine in a rat model of arteriosclerosis induced by long-term inhibition of nitric oxide synthesis

Amlodipine (a new class of calcium channel antagonist) has been shown to limit the progression of arteriosclerosis and decrease the incidence of cardiovascular events. The mechanisms underlying the beneficial effects of amlodipine, however, remain unclear. Therefore, we hypothesized that amlodipine attenuates the development of arteriosclerosis through the inhibition of inflammation in vivo. Long-term inhibition of nitric oxide (NO) by administration of a NO synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME), to rats induces coronary vascular inflammation [monocyte infiltration, monocyte chemoattractant protein-1 (MCP-1) expression, increased activity of angiotensin-converting enzyme (ACE)], and arteriosclerosis. Here, we used the rat model to investigate the anti-inflammatory effects of amlodipine in vivo. Treatment with amlodipine markedly inhibited the L-NAME-induced increase in vascular inflammation, oxidative stress, and local ACE and Rho activity and prevented arteriosclerosis. Interestingly, amlodipine prevented the L-NAME-induced increase in MCP-1 receptor CCR2 expression in circulating monocytes. Amlodipine markedly attenuated the high mortality rate at 8 wk of treatment. These data suggest that amlodipine attenuated arteriosclerosis through inhibiting inflammatory disorders in the rat model of long-term inhibition of NO synthesis. The anti-inflammatory effects of amlodipine seem to be mediated not only by the inhibition of local factors such as MCP-1 but also by the decrease in CCR2 in circulating monocytes. Inhibition of the MCP-1 to CCR2 pathway may represent novel anti-inflammatory actions of amlodipine beyond blood pressure lowering.     

Interaction of charged and uncharged calcium channel antagonists with phospholipid membranes. Binding equilibrium, binding enthalpy, and membrane location.

The membrane location and the binding mechanism of two Ca2+ channel antagonists, amlodipine and nimodipine, in pure lipid membranes were investigated with deuterium and phosphorus-31 nuclear magnetic resonance, with thermodynamic methods such as high-sensitivity titration calorimetry, and by measuring the membrane surface charge via the zeta-potential. The two drugs exhibit quite different physical-chemical properties. The noncharged nimodipine is strongly hydrophobic, and selective deuteration of the lipid membrane reveals a homogeneous distribution of nimodipine across the whole hydrocarbon layer, but no interaction at the lipid headgroup level. The membrane behavior of the amiphiphilic amlodipine (electric charge z = +1) is distinctly more complex. Deuterium magnetic resonance demonstrates that amlodipine adopts a well-defined position in the bilayer membrane. In particular, the charged ethanolamine side group of amlodipine is located near the water-lipid interface, interacting with the dipoles of the headgroup region according to a nonspecific, electrostatic mechanism and inducing a reorientation of the phosphocholine dipoles toward the water phase. At the level of the hydrocarbon segment, the nonpolar ring system of amlodipine interacts specifically with the cis double bond of the membrane lipid, forming a weak association complex. With increasing amlodipine concentration the deuterium signal of the cis double bond gradually loses intensity, a phenomenon previously observed only in related studies on protein-lipid interactions. The binding equilibrium of amlodipine to phosphatidylcholine membranes was studied by measuring the electrophoretic mobility of lipid vesicles and with a centrifugation assay. Hydrophobic interactions of the nonpolar ring systems and electrostatic repulsions at the membrane surface contribute to the binding energy.(ABSTRACT TRUNCATED AT 250 WORDS)     

氨氯地平和硝苯地平临床治疗高血压的有效性与安全性的Meta 分析

目的：探讨氨氯地平和硝苯地平临床治疗高血压的有效性与安全性。方法：计算机检索中国知网、维普资讯网和万方数据库,收集1990—2013 年间国内公开发表的关于氨氯地平和硝苯地平治疗高血压的随机对照试验文献资料,并根据纳入和排除标准,对其进行筛选;采用Stata 12.0 软件对纳入文献中临床试验数据进行Meta 分析。结果：共筛选出23 篇文献。纳入文献中氨氯地平和硝苯地平治疗高血压的有效性Meta 分析结果显示,两药物治疗组有效性总体数据的OR 为2.71（95%CI：2.07,3.55）,且P ＜ 0.01,即氨氯地平组的总有效率显著高于硝苯地平组;安全性Meta 分析结果显示,两药物治疗组安全性总体数据的OR 为0.36（95%CI：0.28,0.47）,且P ＜ 0.01,即氨氯地平组的总不良反应发生率显著低于硝苯地平组。结论：与硝苯地平相比,氨氯地平临床治疗高血压更有效、更安全。     

Detection and determination of total amlodipine by high-performance thin-layer chromatography: a useful technique for pharmacokinetic studies

A novel analytical method for determination of the total plasma levels (free and protein bound) of the calcium channel blocking agent amlodipine has been developed using a high-performance thin-layer chromatographic (HPTLC) procedure. Detection and quantitation were performed without internal standards. In previously described methods for the estimation of amlodipine by gas chromatography and high-performance liquid chromatography, only the free levels in plasma and serum were quantified at 7% of the total amlodipine level, with the remaining 93% bound to plasma protein and tissue. The present method employs proteolysis of the plasma proteins by incubating plasma for 2 h in pepsin solution. After proteolysis amlodipine is extracted and a known amount of the extract is spotted on precoated silica-gel 60 F₂₅₄ plates using a Camag Linomat IV autosampler. Amlodipine was quantified using a dual-wavelength TLC scanner. The method provides a direct estimate of the total amlodipine present in plasma.     

Obtaining antibodies to 1,4-dihydropyridine calcium channel blockers

Immunization of rabbits with amlodipine conjugated with horseradish peroxidase resulted in raising polyclonal antibodies that allowed group determination of 1,4-dihydropyridine calcium channel blockers in aqueous solutions by ELISA with a sensitivity of 0.1 to 1.0 ng/ml for amlodipine, felodipine, nifedipine, and isradipine.     

The influence of amlodipine and verapamil on ion and water transport in the nephron, skin and urinary bladder of amphibians.

1. The addition of amlodipine or verapamil into the lumen of the newt distal tubule led to the decrease of reabsorption of Na, Cl, Ca and of fluid. 2. The application of amlodipine to the outside of the frog skin caused large increases in potential difference (PD) and short circuit (SCC) similar to what is seen with Co2+. If both amlodipine and Co2+ were applied simultaneously to the outer surface the increases in PD and SCC were additive. 3. Verapamil added to the outer surface of the skin caused a reduction in PD which could be overcome by subsequent addition of amlodipine. 4. After addition of amlodipine to serosal or mucosal surfaces of the frog urinary bladder, the ability of vasopressin to increase osmotic permeability was markedly attenuated. 5. It is likely that the calcium channel blockers used here not only affect intracellular calcium levels by inhibiting entry through calcium channels, but they may also alter calcium dependent processes within the plasma membranes which modulate sodium transfer across epithelia.     

Amlodipine decreases fibrosis and cardiac hypertrophy in spontaneously hypertensive rats: persistent effects after withdrawal

Our objective was to examine the effect of chronic treatment with amlodipine on blood pressure, left ventricular hypertrophy, and fibrosis in spontaneously hypertensive rats and the persistence of such an effect after drug withdrawal. We investigated the effects of treatment with 2, 8 and 20 mg/kg/day of amlodipine given orally for six months and at three months after drug withdrawal. Systolic blood pressure was measured using the tail-cuff method. At the end of the study period, the heart was excised, the left ventricle was isolated, and the left ventricle weight/body weight ratio was calculated as a left ventricular hypertrophy index. Fibrosis, expressed as collagen volume fraction, was evaluated using an automated image-analysis system on sections stained with Sirius red. Age-matched untreated Wistar-Kyoto and SHR were used as normotensive and hypertensive controls, respectively. Systolic blood pressure was reduced in the treated SHR in a dose-dependent way and after amlodipine withdrawal it increased progressively, without reaching the values of the hypertensive controls. Cardiac hypertrophy was reduced by 8 and 20 mg/kg/day amlodipine, but when treatment was withdrawn only the group treated with 8 mg/kg/day maintained significant differences versus the hypertensive controls. All three doses of amlodipine reduced cardiac fibrosis and this regression persisted with the two highest doses after three months without treatment. We concluded that antihypertensive treatment with amlodipine is accompanied by a reduction in left ventricular hypertrophy and regression in collagen deposition. Treatment was more effective in preventing fibrosis than in preventing ventricular hypertrophy after drug withdrawal.     

氨氯地平联合美托洛尔治疗原发性高血压的临床疗效观察

目的：观察氨氯地平联合美托洛尔治疗高血压的临床效果及安全性。方法：对2012年4月至2012年11月期间在我科住院治疗的102例患者随机分成两组,对照组接受氨氯地平治疗,治疗组在对照组的基础上使用美托洛尔治疗,分析比较两组的疗效。结果：治疗组和对照组的血压以及心率较治疗前明显降低,差异有统计学意义（P〈0．01）;治疗组治疗后的舒张压与对照组治疗后的舒张压相比,差异有统计学意思（P〈0．01）;治疗组的总有效率高于对照组（P〈0．05）;治疗组的副反应低于对照组（P〈0．05）。结论：氨氯地平联合美托洛尔治疗高血压效果显著,优于单纯应用氨氯地平。     

Ameliorating effects of amlodipine on plasma and myocardial catecholamines in BIO 53.58 Syrian hamsters, a model of dilated cardiomyopathy

Our previous study has shown that the concentrations of norepinephrine, epinephrine and dopamine in the plasma of BIO 53.58 hamsters (a model of dilated cardiomyopathy: DCM) at 18 weeks of age (severe cardiomyopathic stage) were twice those of age-matched F1B control and conversely the myocardial norepinephrine level was decreased. The present study was undertaken to examine the effect of amlodipine on catecholamine concentration, myocardial receptors and histopathological changes in BIO 53.58 hamsters. Oral administration of amlodipine (10 mg/kg/day) for 7 weeks in 11 week-old-BIO 53.58 hamsters brought about marked decreases in the concentrations of norepinephrine, epinephrine and dopamine in the plasma, compared with those in vehicle-treated BIO 53.58 hamsters. This was accompanied by a concomitant increase in the concentration of myocardial catecholamine concentration. In other words, the concentrations of catecholamines in plasma and myocardium of amlodipine administered BIO 53.58 hamsters approximated to the control level in age-matched F1B. In addition, amlodipine administration caused a significant reduction of calcium deposition with a tendency toward a decrease in the myocardial necrosis, and it had little effect on the affinity and number of specific binding for (+)-[3H]PN 200-110, (-)-[125I]iodocyanopindolol (CYP) and [3H]prazosin in the myocardium. In conclusion, the present study shows that administration of amlodipine in BIO 53.58 hamsters may exhibit ameliorating effect on plasma and myocardial catecholamines with a significant reduction of calcium deposition. These data may offer further support for the use of amlodipine in patients with DCM.     

A calcium channel blocker activates both ecto-5(')-nucleotidase and NO synthase in HUVEC

Since amlodipine, a long-acting Ca channel blocker, increases both NO and adenosine production in canine hearts, we investigated that amlodipine activates both ecto-5(')-nucleotidase responsible for adenosine production and NO synthase (NOS) for NO production in human umbilical venous endothelial cells (HUVECs), and its cellular signaling. We measured activities of ecto-5(')-nucleotidase and NOS in HUVECs in the condition with additions of xanthine (100 microM)+xanthine oxidase (1.6 x 10(-3)U/ml) in the presence or absence of amlodipine (1 x 10(-9)-1 x 10(-6)M). Amlodipine increased both ecto-5(')-nucleotidase and NOS activities. Xanthine+xanthine oxidase deactivated both NOS and ecto-5(')-nucleotidase, and amlodipine increased both activities of NOS and ecto-5(')-nucleotidase by 117+/-33% and 48+/-6%, respectively. Amlodipine phosphorylated p38MAP kinase and that an inhibitor of p38MAP kinase inhibited the amlodipine-induced activation of both NOS and ecto-5(')-nucleotidase. Furthermore, amlodipine increased both adenosine and NO production in the canine ischemic hearts. We concluded that amlodipine activates both NOS and ecto-5(')-nucleotidase via p38MAP kinase in vitro and enhances both NO and adenosine production in vivo.     

三氧化二砷联合氨氯地平对肝癌HepG2细胞体外作用的实验研究

目的:探讨三氧化二砷与氨氯地平单独用药及联合用药对肝癌Hep G2细胞增殖和凋亡的作用。方法:用不同浓度的三氧化二砷(4.0、2.0、1.0μmol/L)和氨氯地平(27×103、18×103、12×103 mg/m L)处理体外培养的人肝癌Hep G-2细胞,观察细胞形态的变化,采用CCK-8法检测两种药物单独及联合应用对Hep G-2细胞生长增殖的影响,并通过流式细胞术观察其对细胞凋亡及细胞周期的影响。结果:三氧化二砷和氨氯地平均可以浓度依赖性方式显著增加Hep G2细胞的生长抑制率及其凋亡率,以联合用药的作用较单独用药更显著(P0.05)。与三氧化二砷和氨氯地平单独用药相比,联合用药可显著阻滞Hep G2细胞于G2期及S期。结论:三氧化二砷和氨氯地平均可显著抑制人肝癌Hep G2细胞的生长和增殖,并促进其凋亡,且二者联合应用时具有协同作用。     

Stereoselective plasma protein binding of amlodipine

The binding of the (R)‐ and (S)‐enantiomers of amlodipine to bovine serum albumin (BSA), human serum albumin (HSA), α₁‐acid glycoprotein (AGP), and human plasma (HP) was studied by equilibrium dialysis over the concentration range of 75–200 μM at a protein concentration of 150 μM. Unbound drug concentrations were determined by enantioselective capillary electrophoresis using 50 mM phosphate buffer, pH 2.5, containing 18 mM α‐cyclodextrin as background electrolyte. Saturation of the protein binding sites was not observed over the concentration range tested. Upon application of racemic amlodipine besylate, (S)‐amlodipine was bound to a higher extend by HSA and HP compared with (R)‐amlodipine, whereas the opposite binding of the enantiomers was observed for BSA and AGP. Scatchard analysis was used to illustrate the different binding affinities of amlodipine besylate enantiomers to BSA, HSA and AGP. Chirality, 2010. © 2009 Wiley‐Liss, Inc.     

Amlodipine ameliorates myocardial hypertrophy by inhibiting EGFR phosphorylation

The effects of long-acting calcium channel blockers on pressure overload-induced cardiac hypertrophy have been little studied in experimental animals and the underlying mechanisms are not fully understood. We previously reported that cardiomyocyte hypertrophy could be induced via phosphorylation of the epidermal growth factor receptor (EGFR). In this study, we investigated whether amlodipine attenuates cardiac hypertrophy by inhibiting EGFR phosphorylation. We found that amlodipine dose-dependently inhibited epinephrine-induced protein synthesis and EGFR phosphorylation in cultured neonatal rat cardiomyocytes. Our in vivo study revealed that amlodipine could ameliorate myocardial hypertrophy induced by transverse aortic constriction (TAC) in C57/B6 mice. One week after TAC, amlodipine treatment (3 mg/kg/day) significantly reduced the heart-to-body weight ratio (6.04 +/- 0.16 mg/g vs. 6.90 +/- 0.45 mg/g in untreated TAC mice, P < 0.01). These results indicate that amlodipine ameliorates cardiomyocyte hypertrophy via inhibition of EGFR phosphorylation.     

Long-term use of angiotensin II receptor antagonists and calcium-channel antagonists in Algerian hypertensive patients: Effects on metabolic and oxidative parameters

The effects of calcium antagonists (amlodipine) and angiotensin II receptor antagonists (telmisartan) on lipid profile and oxidative markers were investigated in Algerian hypertensive patients. At the beginning and after 1 year of antihypertensive therapy, blood samples are collected for determination of biochemical parameters (glucose, cholesterol, triglycerides, urea, creatinine) and oxidative markers (malondialdehyde, carbonyl proteins, nitric oxide, superoxide anion, vitamin C, glutathione, catalase, superoxide dismutase). The results of this study indicate that telmisartan and amlodipine are effective antihypertensive agents in the treatment of hypertension because a significant reduction in systolic and diastolic blood pressure was observed in all hypertensive patients after 1 year of treatment. Our results show also that telmisartan and amlodipine treatments counteracted hypertension-dependent lipid abnormalities and oxidative stress. Telmisartan treatment appears to be more efficient than amlodipine treatment. In addition, telmisartan, which reversed all lipid and redox changes associated with hypertension, should be prescribed, especially in hypertensive patients with hypertriglyceridemia and with severe oxidative stress.     

Ionization, lipophilicity, and molecular modeling to investigate permeability and other biological properties of amlodipine

This paper uses a recent approach toward drug discovery, in which in silico tools and experimental data are combined together to study the structural features of amlodipine and their relevance in the peculiar pharmacodynamic and pharmacokinetic profiles of this long acting calcium antagonist. Results reveal for amlodipine two families of conformers (folded and extended) but also demonstrate that protonation is the predominant factor governing amlodipine intermolecular interactions among which ionic forces play a major role.     

ANP在大鼠高血压进展为心力衰竭中的作用

目的：探讨心房钠尿钛ANP 在高血压心力衰竭发展过程中的变化和氨氯地平保护心肌细胞的作用。方法：对大鼠行腹主动 脉结扎术，术后随机选择40 只大鼠分为氨氯地平（中、高、低剂量）组以及模型组，另外选取10 只健康雄性SD 大鼠作为假手术 组。采用ELISA 方法检测各组血清ANP 浓度变化。结果：随着心功能不全加重，ANP 水平逐渐上升。氨氯地平用药组大鼠的心功 能改善明显优于模型组，ANP 明显降低，且随着氨氯地平用药量上升，心功能不断改善，ANP显著下降，P<0.05。结论：对血清 ANP浓度进行测定能够反映出高血压大鼠模型心室功能不全及充血性心力衰竭严重程度。而氨氯地平能够影响机体的ANP 分 泌对心肌细胞起到保护作用，从而有效抑制心室重构，延缓高血压心力衰竭疾病进展。