钙通道阻滞剂对甲亢性高血压大鼠胸主动脉舒张反应的影响

目的探讨T型和L型钙通道阻滞剂对甲亢性高血压大鼠离体胸主动脉舒张反应的影响。方法大鼠皮下每天注射甲状腺素(T4)0.5mg.kg-1的剂量或等体积的生理盐水维持16d,制备甲亢性高血压大鼠模型组和对照组。采用甲亢性高血压大鼠模型组和对照组的大鼠离体胸主动脉血管环标本,观察T型钙通道阻滞剂mibefradil(mibe)和L型钙通道阻滞剂diltiazem(dilt)对两组大鼠胸主动脉血管环舒张反应的影响。结果与对照组相比,甲亢性高血压大鼠体重明显下降而心率和收缩压明显升高;胸主动脉血管细胞外膜明显增厚,平滑肌细胞核变大并排列不规则。甲亢性高血压疾病时,T型和L型钙通道阻滞剂对胸主动脉的舒张作用明显增强。结论甲亢性高血压病理状态下,胸主动脉T型和L型钙通道的功能增强,可能成为治疗甲亢性高血压的药物靶点。     

白杨素对大鼠离体肾动脉的舒张作用

目的研究白杨素对大鼠离体肾动脉的舒张作用及其机制是否涉及抑制肾动脉血管平滑肌细胞L-型电压依赖性钙通道。方法利用微血管张力记录仪(DMT)观察白杨素对预收缩大鼠肾动脉血管环的肌源性反应;利用全细胞膜片钳电生理学实验方法,观察白杨素对大鼠离体肾动脉血管平滑肌细胞L-型电压依赖性钙电流的作用。结果 1白杨素浓度依赖性的舒张60 mmol/L KCl或10-5 mol/L去氧肾上腺素(PE)预收缩的大鼠肾动脉血管环,其最大舒张幅度分别为88.99%和67.47%,RC50值分别为26.25μmol/L和51.68μmol/L。2白杨素(浓度为RC50值)可抑制大鼠肾动脉血管平滑肌细胞L-型电压依赖性钙电流,使其I-V曲线非平行上移;给予0 mV单电压刺激时,白杨素(浓度为RC50值)使大鼠肾动脉血管平滑肌细胞L-型电压依赖性钙电流值降低45.43%。结论 1白杨素浓度依赖性舒张60 mmol/L KCl或10-5 mol/L PE预收缩的大鼠肾动脉血管环;2白杨素抑制大鼠肾动脉血管平滑肌细胞L-型电压依赖性钙电流,使其I-V曲线非平行上移。     

电压依赖性钙通道的α2δ亚基和疾病及药物靶点的关系

目的介绍电压依赖性Ca2 通道(Cav)的亚单位之一α2δ的结构和功能以及与疾病的关系。方法对近期文献进行综述。结果电压依赖性Ca2 通道由5个亚单位组成。α2δ亚基由α2与δ亚基联接,共同对组成通道孔道的α1亚基进行辅助,以调解外钙内流。介绍了α2δ亚基的结构和在体内的分布,以及与疾病的关系(尤其是癫痫、偏头痛和神经源性疼痛)。gabapentin类药物是α2δ1和α2δ2亚基的小分子配体,通过α2δ亚基起治疗作用。结论α2δ亚基与疾病有关联,也是电压依赖性钙通道的分子靶点,值得进一步研究。     

T型钙通道和心血管及神经系统疾病

低电压T型钙通道广泛分布在各种类型细胞中,包括心血管和神经元细胞中,与高电压钙通道不同,在接近膜静息电位的低度去极化时即能被激活,因而有利于心脏起博和神经元细胞在生理状态下接近静息时,对兴奋和电反应的调节。但对T型钙通道在疾病中的作用所知有限。近年来因为克隆出3种T型钙通道α1亚单位的基因,(Cav3.1,Cav3.2和Cav3.3),使深入研究实验动物及人体疾病时T型钙通道的性质、药理、体内分布、基因调节成为可能。并且为新药研发提供有力工具。转基因动物实验已证明T型钙通道不仅是治疗肾性高血压、心律失常也是治疗意识丧失型癫痫及神经性疼痛的重要药物靶点。此外,细胞内钙超载还与房颤、心衰、偏头痛、阿尔采末病、睡眠障碍等的发病有关,所以盼望有新的T型钙通道阻断剂出现。有报道Efonidipine能选择性地抑制低电压T型钙通道,有望成为选择性阻断剂。此外,近年来调控T型钙通道活性的分子机制的研究取得新的达展,对新药的开发有所启迪。作者建议,对治疗心血管及神经系统疾病的药物靶点T型钙通道及其阻断剂的研究给予更多的关注。     

L-型钙通道阻断剂对曲马多镇痛作用的影响

目的　研究L 型钙通道阻断剂对曲马多镇痛作用的影响。方法　选用小鼠热板实验和醋酸扭体实验作为评价方法。腹腔注射曲马多观察该药在不同模型中的镇痛作用。维拉帕米 ,尼莫地平或硝苯地平分别与阈下剂量曲马多合用 ,观察这 3种L 型钙通道阻断剂对曲马多镇痛作用的影响。结果　热板实验中 ,曲马多 (10 ,2 0 ,4 0mg·kg-1)剂量依赖性地延长小鼠舔后足或跳跃的潜伏期 ;维拉帕米可增强曲马多的镇痛作用。醋酸扭体实验中 ,曲马多 (2 ,5 ,10mg·kg-1)显著减少小鼠扭体反应的次数 ;维拉帕米、尼莫地平和硝苯地平均可剂量依赖性地增强曲马多的镇痛作用。结论　L 型钙通道阻断剂维拉帕米、尼莫地平和硝苯地平对曲马多的镇痛作用有一定的增强作用。L 型钙通道介导的胞外钙内流可能参与了曲马多的镇痛机制     

Cav1.2钙离子通道三维结构的同源建模及其应用

目的构建心肌Cav1.2钙离子通道三维结构模型,检验模型的准确性与可靠性。方法利用SWISS-MODEL同源建模服务器,对豚鼠心肌细胞Cav1.2通道α1亚基进行同源建模,建模结果提交至加州大学蛋白质结构在线检测服务器进行检测评估,并对结构模型进行打分。利用MOE软件分子对接程序模拟阻断剂或药物与Cav1.2通道模型的结合,进一步验证通道模型的准确性与可靠性。结果在SWISS-MODEL服务器上搜寻到的模板序列Cav1.1α1S与目标序列Cav1.2α1C均为L型钙通道,序列比对结果显示其同源性高达71.5%,选择自动模式(automated mode)进行同源建模。L型钙通道阻断剂维拉帕米、硝苯地平、地尔硫卓能结合到Cav1.2通道三维结构模型的特定区域,而钠通道特异性阻断剂河豚毒素并未与该模型相结合,中药有效成份白花前胡甲素和小檗碱与该模型也有一定的结合。结论成功构建了心肌Cav1.2钙离子通道三维结构模型,为后续研究提供了可靠样本,也为同源建模在研究离子通道三维结构预测中的应用奠定了基础。     

胍丁胺对大鼠心室肌细胞L—钙通道电流的影响

目的:观察胍丁胺(Agm)对大鼠心室肌细胞L-型钙通道电流(I_(Ca-L))的影响.方法:以酶解法制备单个心室肌细胞.应用全细胞膜片箝技术记录大鼠单个心室肌细胞钙通道电流.结果:(1)Agm(0.5,1,2mmol/L)可浓度依赖性地降低电压依赖性激活I_(Ca-L)(pA)峰值,其值从1451±236 (对照组)到937±105(n=8,P<0.05),585±74(n=8,P<0.01),和301±156(n=8,P<0.01).(2)Agm 1 mmol/L使用依赖性地阻滞I_(Ca-L)·1 Hz时抑制率为53％±12％(P<0.05),3Hz时为69％±11％(P<0.01).(3)Agm使I-V曲线上移,但对I_(Ca-L)的电压依赖特征、最大激活电压以及I_(Ca-L)稳态激活无明显影响.在Agm 1 mmol/L作用下,半数激活电压(V_(0.5)和斜率参数(k)与对照组相比均无显著性差异.V_(0.5)分别为(-20.2±2.5)mV和(-20.5±2.7)mV,k分别为(3.2±0.4)mV和(3.0±0.5)mV.(4)Agm 1 mmol/L可明显使钙电流稳态失活曲线左移,加速钙通道电压依赖性稳态失活.V_(0.5)分别为(-32±6)mV和(-40±5)mV,k分别为(7.6±O.9)mV和(12.5±1.1)mV(P<0.05).(5)Agm 1mmol/L还使I_(Ca)从失活状态下恢复明显减慢.结论:Agm抑制I_(Ca-L),并主要作用于L-型钙通道的失活状态,表现为钙通道失活加速和从失活状态下恢复减慢.     

钙通道阻断剂的合理应用

钙通道阻断剂(Caicium channel Blcokers)可抑制心肌和平滑肌中钙的注入,并且广泛地应用于冠状动脉疾病,某些室上性心律失常和高血压等疾病。下面就目前临床常用的硫氮卓酮(Diltazem);心痛定(硝苯吡啶Nifdpine:和异搏定(戊脉安、Verapamil)三种钙通道阻断剂的药代动力学、药理学、副作用结合临床应用经验给予评述,以便更好地应用此类药物。 1 药代动力学:钙通道阻断剂相对药代动力学参数的平均值见表1。这些药物在胃肠道给药,都能很好吸收,而且主要在肝脏代谢,所以,第一通过效应时,所有这些药物的生物利用     

L型钙通道的新配体

至少有3种电压依赖性钙通道:L,N 和T 型。L 型钙通道是一个大的复合蛋白,可分为5个亚基,上面可能有多个药物结合位点。虽然临床上有代表性的主要药物维拉帕米、硝苯啶、地尔硫(艹卓)是与 L 型钙通道上3个主要的、独立的位点结合,但一些新药却很有可能是作用于其它位点来调节通道的活动的。     

新型抗高血压药物盐酸埃他卡林对小动脉的选择性扩张作用及其药理学机制

目的 :研究新型抗高血压药物盐酸埃他卡林(Ipt)对小动脉的作用特性及其药理学机制。方法 :采用大鼠尾动脉螺旋状血管条和主动脉离体血管环两种组织 ,对比观察盐酸埃他卡林对大、小动脉扩张作用的药理学特性 ,并且利用膜片钳技术观察盐酸埃他卡林对大鼠尾动脉平滑肌细胞钾电流的影响。结果 :Ipt在 1 0 - 7～ 1 0 - 3 mol·L- 1范围内对KCl预致收缩的大鼠尾动脉血管条产生剂量依赖性舒张反应 ,且具有部分内皮依赖性 ,但对主动脉离体血管环无明显的舒张反应 ,该作用在高血压状态时显著增强 ,能被ATP敏感性钾通道特异性阻断剂格列苯脲阻断 ,并且对大鼠尾动脉平滑肌细胞的钾电流具有显著增强作用。结论 :盐酸埃他卡林具有选择性舒张小动脉作用 ,具有ATP敏感性钾通道开放剂的主要药理学特征     

Vascular effects of calcium channel antagonists: new evidence

Calcium channel antagonists have a well-established role in the management of cardiovascular diseases. L-type calcium channels in vascular cells are a key therapeutic target in hypertension and are the preferred molecular target of the initial calcium channel antagonists. However, third-generation dihydropyridine (DHP) calcium channel antagonists, including manidipine, nilvadipine, benidipine and efonidipine, appear to have effects in addition to blockade of the L-type calcium channel. Voltage-gated calcium channels are widely expressed throughout the cardiovascular system. They constitute the main route for calcium entry, essential for the maintenance of contraction. Cardiac and vascular cells predominantly express L-type calcium channels. More recently, T-type channels have been discovered, and there is emerging evidence of their significance in the regulation of arterial resistance. A lack of functional expression of L-type channels in renal efferent arterioles may be consistent with an important role of T-type channels in the regulation of efferent arteriolar tone. Although the exact role of T-type calcium channels in vascular beds remains to be determined, they could be associated with gene-activated cell replication and growth during pathology. The three major classes of calcium channel antagonists are chemically distinct, and exhibit different functional effects depending on their biophysical, conformation-dependent interactions with the L-type calcium channel. The DHPs are more potent vasodilators, and generally have less cardiodepressant activity than representatives of other classes of calcium channel antagonist such as diltiazem (a phenylalkylamine) and verapamil (a benzothiazepine). In contrast to older calcium channel antagonists, the newer DHPs, manidipine, nilvadipine, benidipine and efonidipine, dilate not only afferent but also efferent renal arterioles, a potentially beneficial effect that may improve glomerular hypertension and provide renoprotection. The underlying mechanisms for the heterogenous effects of calcium channel antagonists in the renal microvasculature are unclear. A credible hypothesis suggests a contribution of T-type calcium channels to efferent arteriolar tone, and that manidipine, nilvadipine and efonidipine inhibit both L and T-type channels. However, other mechanisms, including an effect on neuronal P/Q-type calcium channels (recently detected in arterioles), the microheterogeneity of vascular beds, and other types of calcium influx may also play a role. This article presents recent data about the expression and physiological role of calcium channels in arteries and the molecular targets of the calcium channel antagonists, particularly those exhibiting distinct renovascular effects.     

Regulation of Cav1.2 current: interaction with intracellular molecules

Ca(V)1.2 (alpha(1c)) is a pore-forming subunit of the voltage-dependent L-type calcium channel and is expressed in many tissues. The beta and alpha(2)/delta subunits are auxiliary subunits that affect the kinetics and the expression of Ca(V)1.2. In addition to the beta and alpha(2)/delta subunits, several molecules have been reported to be involved in the regulation of Ca(V)1.2 current. Calmodulin, CaBP1 (calcium-binding protein-1), CaMKII (calcium/calmodulin-dependent protein kinase II), AKAPs (A-kinase anchoring proteins), phosphatases, Caveolin-3, beta(2)-adrenergic receptor, PDZ domain proteins, sorcin, SNARE proteins, synaptotagmin, CSN5, RGK family, and AHNAK1 have all been reported to interact with Ca(V)1.2 and the beta subunit. This review focuses on the effect of these molecules on Ca(V)1.2 current.     

Pathophysiological significance of T-type Ca2+ channels: role of T-type Ca2+ channels in renal microcirculation

Since conventional Ca(2+) antagonists, with predominant blockade of L-type voltage-dependent Ca(2+) channels, elicit preferential dilation of afferent arterioles, they might ostensibly aggravate glomerular hypertension. Recently, novel Ca(2+) antagonists, with inhibitory action on L-/T-type Ca(2+) channels, have been reported to dilate both afferent and efferent arterioles. The present review attempted to characterize the renal action of these Ca(2+) antagonists and evaluated the consequences following the treatment with these agents. In contrast to conventional Ca(2+) antagonists (e.g., nifedipine), novel antagonists (e.g., benidipine, efonidipine) potently dilated afferent and efferent arterioles; their action on efferent arterioles appeared to be mediated by the T-type Ca(2+) channel blockade, probably through the inhibition of the intracellular Ca(2+) release. The comparison of the anti-proteinuric action in subtotally nephrectomized rats showed that efonidipine exerted more prominent action than nifedipine. Furthermore, Ca(2+) antagonists with T-type Ca(2+) inhibitory action inhibited renin/aldosterone release and proinflammatory process. Finally, patients with chronic renal disease given a 48-week efonidipine treatment showed reduced proteinuria, and this effect was seen even when mean arterial blood pressure failed to become less than 100 mmHg. Collectively, T-type Ca(2+) channel blockade provides beneficial action in renal injury. Various mechanisms serve to protect against renal injury, including systemic/glomerular hemodynamic action and non-hemodynamic mechanisms.     

Chronic morphine treatment decreases the Cav1.3 subunit of the L-type calcium channel

Voltage-gated L- and N-type calcium channels (VOCs) are implicated in the activity of morphine, but their contribution to the expression of opioid tolerance remains uncertain. L- and N-type VOCs are heteropentamers of alpha(1), alpha(2)delta, beta, and gamma subunits. The alpha(1) subunit forms both the ion pore and the binding site for ligands. The Ca(v)1.2 and Ca(v)1.3 are the neuronal dihydropyridine (DHP)-sensitive L-type channel subunit types. The Ca(v)2.2 subunit is found in omega conotoxin GVIA-sensitive N-type calcium channels. Ca(v)1.2 VOC gating properties are phosphorylation-dependent with many kinases implicated. We hypothesized that changes in channel subunit structure or phosphorylation state, induced by chronic opioid exposure, may in part explain changes in calcium regulation observed both in vivo and in vitro. Antibodies, specific for the Ca(v)1.2, Ca(v)1.3, and Ca(v)2.2 subunits of VOCs were employed with Western immunoassays to access whether chronic morphine treatment had an effect on receptor protein levels. The L-type channel Ca(v)1.3 protein, but not the Ca(v)1.2 protein or phosphorylation state, significantly decreased upon chronic morphine treatment. The Ca(v)2.2 subunit protein of the N-type channel of VOCs remained unchanged. The Ca(v)1.3 subunit modification may represent one of many potential adaptive changes in tolerance to morphine-induced changes in intracellular calcium.     

Vascular calcium channels and high blood pressure: pathophysiology and therapeutic implications

Long-lasting Ca(2+) (Ca(L)) channels of the Ca(v)1.2 gene family are heteromultimeric structures that are minimally composed of a pore-forming alpha(1C) subunit and regulatory beta and alpha(2)delta subunits in vascular smooth muscle cells. The Ca(L) channels are the primary pathways for voltage-gated Ca(2+) influx that trigger excitation-contraction coupling in small resistance vessels. Notably, vascular smooth muscle cells of hypertensive rats show an increased expression of Ca(L) channel alpha(1C) subunits, which is associated with elevated Ca(2+) influx and the development of abnormal arterial tone. Indeed, blood pressure per se appears to promote Ca(L) channel expression in small arteries, and even short-term rises in pressure may alter channel expression. Membrane depolarization has been shown to be one stimulus associated with elevated blood pressure that promotes Ca(L) channel expression at the plasma membrane. Future studies to define the molecular processes that regulate Ca(L) channel expression in vascular smooth muscle cells will provide a rational basis for designing antihypertensive therapies to normalize Ca(L) channel expression and the development of anomalous vascular tone in hypertensive pathologies.     

Mechanisms of oxygen sensing: a key to therapy of pulmonary hypertension and patent ductus arteriosus

Specialized tissues that sense acute changes in the local oxygen tension include type 1 cells of the carotid body, neuroepithelial bodies in the lungs, and smooth muscle cells of the resistance pulmonary arteries and the ductus arteriosus (DA). Hypoxia inhibits outward potassium current in carotid body type 1 cells, leading to depolarization and calcium entry through L-type calcium channels. Increased intracellular calcium concentration ([Ca+ +]i) leads to exocytosis of neurotransmitters, thus stimulating the carotid sinus nerve and respiration. The same K+ channel inhibition occurs with hypoxia in pulmonary artery smooth muscle cells (PASMCs), causing contraction and providing part of the mechanism of hypoxic pulmonary vasoconstriction (HPV). In the SMCs of the DA, the mechanism works in reverse. It is the shift from hypoxia to normoxia that inhibits K+ channels and causes normoxic ductal contraction. In both PA and DA, the contraction is augmented by release of Ca+ + from the sarcoplasmic reticulum, entry of Ca+ + through store-operated channels (SOC) and by Ca+ + sensitization. The same three 'executive' mechanisms are partly responsible for idiopathic pulmonary arterial hypertension (IPAH). While vasoconstrictor mediators constrict both PA and DA and vasodilators dilate both vessels, only redox changes mimic oxygen by having directly opposite effects on the K+ channels, membrane potential, [Ca(++)]i and tone in the PA and DA. There are several different hypotheses as to how redox might alter tone, which remain to be resolved. However, understanding the mechanism will facilitate drug development for pulmonary hypertension and patent DA.     

Adenosine: A natural modulator of L-type calcium channels in atrial myocardium?

The mechanism of action of adenosine at the level of atrial myocardium has been a matter of debate. Electrophysiological studies showed that adenosine increases K+ efflux which may reduce Ca2+ influx, indirectly, by shortening the myocardial action potential. Recently some authors proposed that adenosine also depresses Ca2+ influx by a direct action on the L calcium channel, but, this effect being lower than that on voltage-dependent K+ channels, it was considered of minor importance. The effect of adenosine and its stable analogues was studied in the presence of the dihydropyridine Bay K 8644, a highly specific L-type calcium channel agonist, on isolated guinea-pig atria. The inotropic effect of the calcium channel activator was found to be antagonized by adenosine A1-receptor agonists. Binding studies showed that the effect on Bay K 8644 was not due to the interaction between adenosine analogues and dihydropyridines at the level of a common receptor site on L-type Ca2+ channels. Inhibitors of K+ channels did not antagonize the effect of adenosine analogues against Bay K 8644. Experimental conditions aimed to unmask an effect on slow Ca2+ currents (i.e. K+ depolarized paced atria), further supported that adenosine analogues may act in atria as negative modulators on L-type Ca2+ channels. Finally, the use of 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), a highly specific A1-receptor antagonist, demonstrated that the antagonism of Bay K 8644 by adenosine analogues is strictly dependent on A1 receptors. The above data support the possibility of a dual signal transduction pathway to ion channels (K+ and Ca2+) linked to A1 receptors in atrial myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Requirement for functional BK channels in maintaining oscillation in venomotor tone revealed by species differences in expression of the β1 accessory subunits

We determined the possible role of large-conductance Ca2+-activated K (BK) channels in regulation of venous tone in small capacitance veins and blood pressure. In rat mesenteric venous smooth muscle cells (MV SMC), BK channel α- and β1-subunits were coexpressed, unitary BK currents were detected, and single-channel currents were sensitive to voltage and [Ca2+]i. Rat MV SMCs displayed Ca sparks and iberiotoxin-sensitive spontaneous transient outward currents. Under resting conditions in vitro, rat MV exhibited nifedipine-sensitive spontaneous oscillatory constrictions. Blockade of BK channels by paxilline and Ca2+ sparks by ryanodine constricted rat MV. Nifedipine caused venodilation and blocked paxilline-induced, KCl-induced (20 mM), and BayK8644-induced contraction. Acute inhibition of BK channels with iberiotoxin in vivo increased blood pressure and reduced venous capacitance, measured as an increase in mean circulatory filling pressure in conscious rats. BK channel α-subunits and L-type Ca2+ channel α1-C subunits are expressed in murine MV. However, these channels are not functional because murine MV lack nifedipine-sensitive basal tone and rhythmic constrictions. Murine MV were also insensitive to paxilline, ryanodine, KCl, and BayK8644, consistent with our previous studies showing that murine MV do not have BK β1-subunits. These data show that not only there are species-dependent properties in ion channel control of venomotor tone but also BK channels are required for rhythmic oscillations in venous tone.     

Different effects of L-type and L+N-type calcium channel blockers on hamster cheek pouch venules

Dihydropyridine calcium channel blockers are not uniform in terms of their action on calcium channel. L-type calcium channel blockers dilate the resistance arterioles. Cilnidipine is a dihydropyridine calcium channel blocker that also acts on N-type calcium channels, and may dilate venules through its effect on the sympathetic receptor. The influence of an L-type calcium channel blocker (nifedipine) or this L+N type blocker at 10(-7) mol to 10(-4) mol on venular diameter was examined by superfusion of male Syrian hamster cheek pouches. Nifedipine dose dependently dilated the arterioles alone, whereas cilnidipine dilated both arterioles and venules. Application of 10(-7) mol omega conotoxin, an inhibitor of N-type channels, after nifedipine led to significant dilation of venules, while it had no influence when administered after cilnidipine. These findings indicate that the effects of calcium channel blockers on the venules differ according to the action on N-type calcium channels, and that cilnidipine (an L+N type calcium channel blocker) dilates venules through its additional action on N-type channels.     

Blockade of T-type voltage-dependent Ca2+ channels by benidipine, a dihydropyridine calcium channel blocker, inhibits aldosterone production in human adrenocortical cell line NCI-H295R

Benidipine, a long-lasting dihydropyridine calcium channel blocker, is used for treatment of hypertension and angina. Benidipine exerts pleiotropic pharmacological features, such as renoprotective and cardioprotective effects. In pathophysiological conditions, the antidiuretic hormone aldosterone causes development of renal and cardiovascular diseases. In adrenal glomerulosa cells, aldosterone is produced in response to extracellular potassium, which is mainly mediated by T-type voltage-dependent Ca2+ channels. More recently, it has been demonstrated that benidipine inhibits T-type Ca2+ channels in addition to L-type Ca2+ channels. Therefore, effect of calcium channel blockers, including benidipine, on aldosterone production and T-type Ca2+ channels using human adrenocortical cell line NCI-H295R was investigated. Benidipine efficiently inhibited KCl-induced aldosterone production at low concentration (3 and 10 nM), with inhibitory activity more potent than other calcium channel blockers. Patch clamp analysis indicated that benidipine concentration-dependently inhibited T-type Ca2+ currents at 10, 100 and 1000 nM. As for examined calcium channel blockers, inhibitory activity for T-type Ca2+ currents was well correlated with aldosterone production. L-type specific calcium channel blockers calciseptine and nifedipine showed no effect in both assays. These results indicate that inhibition of T-type Ca2+ channels is responsible for inhibition of aldosterone production in NCI-H295R cells. Benidipine efficiently inhibited KCl-induced upregulation of 11-beta-hydroxylase mRNA and aldosterone synthase mRNA as well as KCl-induced Ca2+ influx, indicating it as the most likely inhibition mechanism. Benidipine partially inhibited angiotensin II-induced aldosterone production, plus showed additive effects when used in combination with the angiotensin II type I receptor blocker valsartan. Benidipine also partially inhibited angiotensin II-induced upregulation of the above mRNAs and Ca2+ influx inhibitory activities of benidipine for aldosterone production. T-type Ca2+ channels may contribute to additional benefits of this drug for treating renal and cardiovascular diseases, beyond its primary anti-hypertensive effects from blocking L-type Ca2+ channels.