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Cav1.2, cell proliferation, and new target in atherosclerosis. ISRN BIOCHEMISTRY 2013; 2013:463527. [PMID: 25937960 PMCID: PMC4392978 DOI: 10.1155/2013/463527] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 03/20/2013] [Indexed: 11/18/2022]
Abstract
Cav1.2 calcium channels are the principal proteins involved in electrical, mechanical, and/or signaling functions of the cell. Cav1.2 couples membrane depolarization to the transient increase in intracellular Ca2+ concentration that is a trigger for muscle contraction and CREB-dependent transcriptional activation. The CACNA1C gene coding for the Cav1.2 pore-forming α1C subunit is subject to extensive alternative splicing. This review is the first attempt to follow the association between cell proliferation, Cav1.2 expression and splice variation, and atherosclerosis. Based on insights into the association between the atherosclerosis-induced molecular remodeling of Cav1.2, proliferation of vascular smooth muscle cells, and CREB-dependent transcriptional signaling, this review will give a perspective outlook for the use of the CACNA1C exon skipping as a new potential gene therapy approach to atherosclerosis.
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2
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Andersson KE. Calcium-entry blockers. A heterogeneous family of compounds. ACTA MEDICA SCANDINAVICA. SUPPLEMENTUM 2009; 694:142-52. [PMID: 3890469 DOI: 10.1111/j.0954-6820.1985.tb08810.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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3
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Andersson KE, Högestätt ED. On the mechanism of action of calcium antagonists. ACTA MEDICA SCANDINAVICA. SUPPLEMENTUM 2009; 681:11-24. [PMID: 6328899 DOI: 10.1111/j.0954-6820.1984.tb08672.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A short review is given of possible mechanisms of action of the organic "calcium antagonists". Calcium antagonists comprise a chemically heterogenous group of drugs, and the term may be used to denote agents that inhibit Ca2+-dependent processes or regulatory mechanisms without acting at other sites. Such drugs may be subdivided into those that decrease the availability of Ca2+ to the myoplasm, and those that decrease the cellular effects of Ca2+ without lowering the intracellular Ca2+ concentration. Accordingly, calcium channel blockers, such as verapamil, nifedipine, and diltiazem, form a subgroup of calcium availability inhibitors, as they block influx of extracellular calcium through ion selective channels in the membrane both in cardiac and smooth muscle. However, it cannot be excluded that some of these drugs, particularly in smooth muscle, may have additional sites of action, which must be taken into consideration when they are used as investigational tools.
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Abstract
The membrane site of action and intracellular effects of diltiazem on heart and blood vessels are briefly discussed and compared to those of other calcium entry blockers, mainly verapamil and nifedipine. Diltiazem seems to have another site of action in the membrane than verapamil and nifedipine. Even if its main action is exerted at the cell membrane level, diltiazem may, at high concentrations, appears to have intracellular effects. Similar to the haemodynamic effects of verapamil and nifedipine, those of diltiazem are determined not only by direct actions on heart and peripheral vessels, but also by sympathetic reflex activity which modulates the direct effects. Two aspects of the myocardial protective action of diltiazem are discussed, the ability of the drug to reduce the frequency of ventricular dysrhythmias associated with ischaemic damage, and the ability to protect the ischaemic myocardium during reperfusion.
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Shevchenko VP, Myasoedov NF, Soldatov NM, Duburs GJ, Kastron VV, Skrastinš IP. Synthesis and evaluation of biological activity of two novel tritium-labeled derivatives of riodipine. J Labelled Comp Radiopharm 2006. [DOI: 10.1002/jlcr.2580270616] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Hockerman GH, Dilmac N, Scheuer T, Catterall WA. Molecular determinants of diltiazem block in domains IIIS6 and IVS6 of L-type Ca(2+) channels. Mol Pharmacol 2000; 58:1264-70. [PMID: 11093762 DOI: 10.1124/mol.58.6.1264] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The benzothiazepine diltiazem blocks ionic current through L-type Ca(2+) channels, as do the dihydropyridines (DHPs) and phenylalkylamines (PAs), but it has unique properties that distinguish it from these other drug classes. Wild-type L-type channels containing alpha(1CII) subunits, wild-type P/Q-type channels containing alpha(1A) subunits, and mutants of both channel types were transiently expressed in tsA-201 cells with beta(1B) and alpha(2)delta subunits. Whole-cell, voltage-clamp recordings showed that diltiazem blocks L-type Ca(2+) channels approximately 5-fold more potently than it does P/Q-type channels. Diltiazem blocked a mutant P/Q-type channel containing nine amino acid changes that made it highly sensitive to DHPs, with the same potency as L-type channels. Thus, amino acids specific to the L-type channel that confer DHP sensitivity in an alpha(1A) background also increase sensitivity to diltiazem. Analysis of single amino acid mutations in domains IIIS6 and IVS6 of alpha(1CII) subunits confirmed the role of these L-type-specific amino acid residues in diltiazem block, and also indicated that Y1152 of alpha(1CII), an amino acid critical to both DHP and PA block, does not play a role in diltiazem block. Furthermore, T1039 and Y1043 in domain IIIS5, which are both critical for DHP block, are not involved in block by diltiazem. Conversely, three amino acid residues (I1150, M1160, and I1460) contribute to diltiazem block but have not been shown to affect DHP or PA block. Thus, binding of diltiazem to L-type Ca(2+) channels requires residues that overlap those that are critical for DHP and PA block as well as residues unique to diltiazem.
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Affiliation(s)
- G H Hockerman
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana, USA.
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Yamamoto N, Nomura M, Okubo K, Maeda K, Goto T. Pharmacologic characterization of FR172516: a new combined calcium channel-blocking and beta-adrenoceptor-blocking agent. J Cardiovasc Pharmacol 1999; 33:587-94. [PMID: 10218729 DOI: 10.1097/00005344-199904000-00011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The pharmacologic characterization of FR172516, a new combined calcium channel-blocking and beta-adrenoceptor-blocking agent, was studied and compared with amlodipine in receptor-binding assay and in vivo studies. In the binding assay, Ki values of FR172516 for calcium channel and beta-receptor were 29.3 nM and 44.1 nM, respectively. In the in vivo studies with pithed rats, FR172516 shifted the dose-response curves of isoproterenol in heart rate to the right, suggesting that this compound has a antiadrenoceptor effect in vivo. The hypotensive effect of FR172516, which could be mainly attributed to its calcium channel-blocking action, was compared with that of amlodipine in normotensive Wistar rats (NTRs), spontaneously hypertensive rats (SHRs), and renal hypertensive dogs (RHDs). FR172516 showed more potent hypotensive action than amlodipine when administered intravenously to NTRs, and apparent bradycardia was seen only with FR172516. In SHRs, FR172516 showed a long-lasting hypotensive action and dose-dependently decreased heart rate, whereas amlodipine scarcely affected heart rate. In RHDs, oral administration of FR172516 once daily for 5 days decreased blood pressure without reflex tachycardia or an increase of plasma renin activity. On the other hand, amlodipine, in the dose at which hypotensive effects equipotent to those of FR172516 were observed, produced apparent reflex tachycardia and concomitant increase of plasma renin. These results indicate that FR172516 has a potent long-lasting antihypertensive effect without activating sympathetic tone by calcium channel-blocking and beta-adrenoceptor-blocking actions.
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Affiliation(s)
- N Yamamoto
- Medicinal Biology Research Laboratory, Fujisawa Pharmaceutical Co., Osaka, Japan
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Kanda S, Kurokawa J, Adachi-Akahane S, Nagao T. Diltiazem derivatives modulate the dihydropyridine-binding to intact rat ventricular myocytes. Eur J Pharmacol 1997; 319:101-7. [PMID: 9030904 DOI: 10.1016/s0014-2999(96)00826-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
To examine whether the modulation of the 1,4-dihydropyridine-binding by diltiazem derivatives, which has been shown in cardiac and skeletal muscle membranes, takes place in intact cardiac myocytes, effects of diltiazem on the specific binding of [3H](+)-PN200-110 to freshly isolated adult rat ventricular myocytes were investigated in normal Tyrode solution at 37 degrees C. Diltiazem consistently potentiated the [3H](+)-PN200-110-binding in a concentration-dependent manner, while DTZ323 (3-(acetyloxy)-5-[2-[[2- (3,4-dimethoxyphenyl)ethyl]-methylamino]ethyl]-2,3-dihydro-2(-4 methoxyphenyl)-1,5-benzothiazepin-4-(5H)-one), a potent diltiazem derivative, inhibited it in a non-competitive manner. In saturation studies, 100 microM decreased the Kd value of the 3[H](+)-PN200-110-binding (control, 0.102 +/- 0.008 vs. diltiazem, 0.074 +/- 0.004 (nM, n = 6), P < 0.05) without significant effect on Bmax (control, 65.7 +/- 6.4 vs. diltiazem, 76.7 +/- 4.4 (fmol/mg protein, n = 6). Moreover, membrane-impermeant quaternary diltiazem also potentiated the [3H](+)-PN200-110-binding in intact myocytes. These results suggest that diltiazem modulates the 1,4-dihydro-pyridine-binding even in intact cardiac myocytes, and the binding site of diltiazem is accessible from the extracellular side of the L-type Ca2+ channels.
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Affiliation(s)
- S Kanda
- Department of Toxicology and Pharmacology, Faculty of Pharmaceuticals Sciences, University of Tokyo, Japan
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Hockerman GH, Peterson BZ, Johnson BD, Catterall WA. Molecular determinants of drug binding and action on L-type calcium channels. Annu Rev Pharmacol Toxicol 1997; 37:361-96. [PMID: 9131258 DOI: 10.1146/annurev.pharmtox.37.1.361] [Citation(s) in RCA: 246] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The crucial role of L-type Ca2+ channels in the initiation of cardiac and smooth muscle contraction has made them major therapeutic targets for the treatment of cardiovascular disease. L-type channels share a common pharmacological profile, including high-affinity voltage- and frequency-dependent block by the phenylalkylamines, the benz(othi)azepines, and the dihydropyridines. These drugs are thought to bind to three separate receptor sites on L-type Ca2+ channels that are allosterically linked. Results from different experimental approaches implicate the IIIS5, IIIS6, and IVS6 transmembrane segments of the alpha 1 subunits of L-type Ca2+ channels in binding of all three classes of drugs. Site-directed mutagenesis has identified single amino acid residues within the IIIS5, IIIS6, and IVS6 transmembrane segments that are required for high-affinity binding of phenylalkylamines and/or dihydropyridines, providing further support for identification of these transmembrane segments as critical elements of the receptor sites for these two classes of drugs. The close proximity of the receptor sites for phenylalkylamines, benz(othi)azepines, and dihydropyridines raises the possibility that individual amino acid residues may be required for high-affinity binding of more than one of these ligands. Therefore, we suggest that phenylalkylamines and dihydropyridines bind to different faces of the IIIS6 and IVS6 transmembrane segments and, in some cases, bind to opposite sides of the side chains of the same amino acid residues. The results support the domain interface model for binding and channel modulation by these three classes of drugs.
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Affiliation(s)
- G H Hockerman
- Department of Pharmacology, University of Washington, Seattle 98195-7280, USA
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10
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Saseen JJ, Carter BL. Dual calcium-channel blocker therapy in the treatment of hypertension. Ann Pharmacother 1996; 30:802-10. [PMID: 8826565 DOI: 10.1177/106002809603000719] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
OBJECTIVE To review the in vitro receptor binding data of calcium-channel blockers (CCBs) and in vivo studies in humans regarding the use of dual calcium-channel blocker therapy, with a focus on the use of this therapy for hypertension. DATA SOURCE A MEDLINE search was conducted to identify literature pertaining to CCBs. STUDY SELECTION In vitro studies and investigations that evaluated CCB receptor binding and the interactions between subclasses of CCBs were chosen. All studies in humans and clinical trials that evaluated the use of dual CCB therapy in the treatment of cardiovascular diseases were selected for review. Also, case reports describing the use of dual CCB therapy were included in this article. DATA EXTRACTION The methodology, results, and conclusions of the selected data were evaluated. Data regarding the in vitro receptor binding kinetics of CCBs, as well as interactions, were reported. Because there is limited information on dual CCB therapy for hypertension, clinical studies using this treatment for ischemic heart disease were also reviewed. They were summarized and compared on the basis of the degree of disease control (e.g., blood pressure, exercise tolerance), adverse effects, and other clinical endpoints of pharmacologic therapy. DATA SYNTHESIS In vitro studies have identified binding sites for the dihydropyridine (nifedipine), diphenylalkylamine (verapamil), and benzothiazepine (diltiazem) subclasses of CCBs, and indicate that they are allosterically related to each other within the voltage-sensitive calcium-channel receptor. Dihydropyridine binding affinity is decreased with concomitant verapamil binding, but is enhanced by concomitant diltiazem binding. Dual CCB therapy has been shown to be efficacious in patients with ischemic heart disease. Although this therapy is limited by dose-related adverse effects, it appears to have an important role in patients with ischemia that is refractory to conventional therapy, or for those whose therapeutic options are limited by contraindications. Theoretically, many patients with hypertension may benefit similarly from dual CCB therapy. Because data evaluating this treatment option are sparse, recommendations regarding safety, efficacy, and the role of dual CCB therapy for hypertension would be premature. CONCLUSIONS Controlled data evaluating dual CCB therapy for the treatment of hypertension are lacking. This treatment modality may be beneficial in the future, but requires further investigation to determine safety and efficacy.
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Affiliation(s)
- J J Saseen
- Department of Pharmacy Practice, School of Pharmacy, University of Colorado Health Sciences Center, Denver 80262, USA
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de Cingolani GE, Mosca SM, Moreyra AE, Cingolani HE. Chronic nifedipine treatment diminishes cardiac inotropic response to nifedifine: functional upregulation of dihydropyridine receptors. J Cardiovasc Pharmacol 1996; 27:240-6. [PMID: 8720423 DOI: 10.1097/00005344-199602000-00010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Chronic treatment with nifedipine induces up-regulation of functional active Ca2+ channels in cardiac muscle membranes. Adult male New Zealand White rabbits (NZW) were treated with nifedipine (20 mg/day) for 25 days. In isovolumic perfused hearts at constant coronary flow and heart rate (HR) the left ventricular developed pressure (LVDP) and its first derivative (dP/dt) were monitored. Basal contractility and contractility at different end-diastolic volumes (EDV) were higher in nifedipine-treated animals, with no changes in diastolic chamber stiffness. Dose response to nifedipine in pretreated animals showed less decrease in contractility than in controls [ED50 = 1.09 +/- 0.09 x 10-7 (control) and 1.55 +/- 0.17 x 10-7 M nifedipine (treated) (p < 0.05)]. Ca2+ channel density was assessed by specific binding at the dihydropyridine receptor with [methyl-3H]PN 200-110. In cardiac membranes, maximal binding capacity (Bmax) was 269 +/- 38 (n = 7, control) and 429 +/- 46 fmol/mg protein (n = 7, treated) (p < 0.05), without significant changes in dissociation constant. In addition, we noted no changes in dihydropyridine (DHP) binding sites in aortic membranes. Our results offer a possible explanation for the lack of decrease in contractility despite the persistent hypotensive effect in hypertensive patients during chronic treatment with nifedipine.
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Affiliation(s)
- G E de Cingolani
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Medicas, La Plata, Argentina
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12
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Matsukado K, Ikezaki K, Nomura T, Fukui M. Effect of calcium antagonists on regional cerebral blood flow in transplanted rat brain tumors. J Neurooncol 1996; 27:1-10. [PMID: 8699220 DOI: 10.1007/bf00146078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We studied the effect of intracarotid infusion of various calcium antagonists on regional CBF (rCBF) in the C6 rat glioma by a hydrogen clearance method. Nimodipine at doses of 0.1, 0.5 and 1 microgram/kg/min was found to produce tumor-specific increases in the rCBF (40.2 +/- 18.4%, p < 0.01, 67.8 +/- 32.6%, p < 0.001 and 37.3 +/- 37.2%, p < 0.05, respectively) without affecting systemic blood pressure. Regarding the time course of the nimodipine effects, at a dose of 0.5 micrograms/kg/min, rCBF in the tumor showed maximum value at fifteen minutes after the start of the intracarotid infusion. Diltiazem at doses of 5, 20, and 40 micrograms/kg/min also increased tumor rCBF in a dose-dependent manner (27.9 +/- 12.5%, p < 0.001, 52.0 +/- 21.8%, p-AN 0.001 and 54.5 +/- 18.4%, p < 0.001, respectively). Both nifedipine and flunarizine significantly increased the rCBF in the tumor, while they did not cause a higher percent increase of the rCBF when compared with those of nimodipine and diltiazem. No significant percent increase of the rCBF in the tumor was observed in verapamil treated rats. These results indicate that tumor vessels may have an altered response to calcium antagonists, especially to nimodipine and diltiazem, when compared to normal brain capillaries. The varied responses to calcium antagonists could be explained by their differences in tissue selectivity and affinity to calcium channels.
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Affiliation(s)
- K Matsukado
- Department of Neurosurgery, Faculty of Medicine, Kyushu University, Fukuoka, Japan
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Ferrante F, Cadoni A, Zaccheo D, Amenta F. Localization of calcium channels of the L-type in human epicardial arteries: a light microscope autoradiographic study. Clin Exp Hypertens 1995; 17:895-912. [PMID: 7581260 DOI: 10.3109/10641969509033642] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The anatomical localization of Ca2+ channels of the L-type was analyzed in sections of the human right and anterior interventricular coronary arteries by using in vitro light microscope autoradiography associated with radioligand binding techniques. [3H]Nicardipine was utilised as a ligand. Binding of the radioligand to sections of the two coronary arteries was time-, temperature- and concentration-dependent. Analysis of binding isotherms revealed a dissociation constant value of about 0.5 nM in the two arteries and maximum binding capacities of 139 +/- 6.4 fmol/mg tissue for the right coronary artery and of 173 +/- 9.5 for the anterior interventricular branch. The pharmacological profile of [3H]nicardipine binding to sections of human coronary arteries was consistent with the labelling of Ca2+ channels of the L-type. Dihydropyridine derivatives were the most powerful competitors of [3H]nicardipine binding, whereas phenylalkylamines, benzothiazepine or non-selective channel modulators were weak competitors or ineffective. Light microscope autoradiography revealed the highest density of [3H]nicardipine binding sites in the tunica media of the coronary arteries. In this layer Ca2+ channels of the L-type are located within smooth muscle cells. A lower accumulation of the radioligand occurred in the tunica adventitia, whereas no specific binding was found in the tunica intima. Study of the localization of Ca2+ channels in sections of human coronary arteries may contribute to a better understanding of the mechanism of the marked coronary dilatory activity elicited by Ca2+ antagonists demonstrable in both in vitro preparations and in vivo.
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Affiliation(s)
- F Ferrante
- Sezione di Anatomia Umana, Università di Camerino, Italy
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Watson WP, Little HJ. Interactions between diltiazem and ethanol: differences from those seen with dihydropyridine calcium channel antagonists. Psychopharmacology (Berl) 1994; 114:329-36. [PMID: 7838926 DOI: 10.1007/bf02244856] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
It has previously been shown that dihydropyridine calcium channel antagonists prevent the ethanol withdrawal syndrome and potentiate the acute effects of ethanol and other central depressant drugs. We now report that, in contrast, the benzothiazepine calcium channel antagonist, diltiazem, gave no protection against the behavioural hyperexcitability seen during ethanol withdrawal, when given either acutely, on withdrawal, or chronically, during the ethanol treatment. A significant increase in convulsive behaviour on handling was seen during the withdrawal period when diltiazem was given on cessation of a mild chronic ethanol treatment schedule. Diltiazem decreased the acute general anaesthetic effects of ethanol, and did not appear to potentiate the ataxic action of ethanol. Centrally administered diltiazem did not enhance the hypothermic action of ethanol, but this effect was significantly increased by diltiazem when the calcium channel antagonist was given peripherally. When given alone by the intraperitoneal route, diltiazem decreased spontaneous locomotor activity and lowered body temperature. When the intracerebral route was used for administration of diltiazem, a significantly decrease in body temperature was seen when this compound was given alone, accompanied by a brief hyperexcitability. The interactions between ethanol and diltiazem therefore appear to differ from those seen with other calcium channel antagonists.
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Affiliation(s)
- W P Watson
- Pharmacology Department, Medical School, University Walk, Bristol, UK
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Guard S, Boyle SJ, Tang KW, Watling KJ, McKnight AT, Woodruff GN. The interaction of the NK1 receptor antagonist CP-96,345 with L-type calcium channels and its functional consequences. Br J Pharmacol 1993; 110:385-91. [PMID: 7693284 PMCID: PMC2176003 DOI: 10.1111/j.1476-5381.1993.tb13821.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1. We investigated the effects of the non-peptide NK1 receptor antagonist, CP-96,345, its inactive enantiomer CP-96,344, and the racemic mixture (+/-)-CP-96,345, on the binding of [3H]-nimodipine and [3H]-diltiazem to L-type calcium channels in rat cerebral cortex membranes. In isolated peripheral tissues containing tachykinin receptors, the effects of (+/-)-CP-96,345 have been compared with those of diltiazem. 2. In guinea-pig trachea, (+/-)-CP-96,345 produced antagonism of responses to the selective NK1 agonists [Sar9, Met(O2)11]SP and substance P-methyl ester that was apparently competitive in nature (pKB 7.0-7.5), while in guinea-pig ileum the antagonism was not surmountable. 3. The reduction of maximum responses by (+/-)-CP-96,345 in the guinea-pig ileum was not selective; it was obtained with muscarinic agonists and other agents, and was also observed in the portal vein of the rat where NK1 receptors are not present. 4. The tissue-specific reduction of maximum responses by (+/-)-CP-96,345 in ileum was reproduced by diltiazem. 5. (+/-)-CP-96,345 produced a concentration-dependent enhancement of [3H]-nimodipine binding to rat cerebral cortex membranes with a maximal stimulation of 186 +/- 29% above control (EC50 83.2 nM). Scatchard analysis revealed that (+/-)-CP-96,345 increased the affinity of [3H]-nimodipine for its binding sites without affecting Bmax (control: KD = 0.32 nM; with 100 nM (+/-)-CP-96,345: KD = 0.074 nM). 6. CP-96,345, CP-96,344, and the racemate all inhibited [3H]-diltiazem binding in rat cerebral cortex membranes with Ki values of 22.5 nM, 34.5 nM and 29.9 nM respectively; a similar value was obtained for diltiazem itself (33.6 nM). In comparison, CP-96,345 and ( +/- )-CP-96,345 inhibited the binding of[125I]-Bolton-Hunter-conjugated substance P in this tissue with Ki values of 59.6 nM and 82.0 nM respectively, while CP-96,344 had no measurable affinity (IC50> 10 microM).7. Substance P and a range of ligands selective for NK1, NK2, or NK3 receptors had no significant effect at 10 microM on either [3H]-diltiazem or [3H]-nimodipine binding.8. The results indicate that in addition to possessing affinity for the NK1 receptor, the non-peptide antagonist, CP-96,345, displays high affinity for [3H]-diltiazem binding sites on L-type calcium channels.The functional effect that may be observed in integrated models will be a consequence of either property, or be a composite effect of NK1 receptor antagonism and L-channel blockade.
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Affiliation(s)
- S Guard
- Parke-Davis Neuroscience Research Centre, Addenbrookes Hospital Site, Cambridge
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Miyoshi K, Kanda A, Miyake H, Ichihara K, Kamei H, Nagasaka M. MPC-1304, another type of dihydropyridine, possessing highly potent vasodilating action. Eur J Pharmacol 1993; 238:139-48. [PMID: 7691619 DOI: 10.1016/0014-2999(93)90841-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We investigated the vasodilating action of MPC-1304, one of the most potent dihydropyridines causing hypotension, in anesthetized dogs and compared this with its binding properties. After intraarterial injection, MPC-1304 was 3 times less potent than other dihydropyridines (nitrendipine, nifedipine, nicardipine and nisoldipine) in increasing femoral blood flow. After infusion of these drugs, however, MPC-1304 was the most potent in increasing femoral blood flow. The onset and recovery of the effect of MPC-1304 on femoral blood flow were slower than for nifedipine. Higher doses of Bay K 8644 were needed to antagonize the stimulating activity of MPC-1304 than for nifedipine. In a competition assay of [3H]nitrendipine binding, MPC-1304 and its metabolites bound to the dihydropyridine receptor with lower affinity than the other dihydropyridines. The binding affinity of [3H]MPC-1304 was lower than that of [3H]nitrendipine, consistent with the potency of this drug to increase femoral blood flow by bolus injection. The association and dissociation of [3H]MPC-1304 was slower than those of [3H]nitrendipine, which is consistent with the slow onset and long-lasting vasodilating effects of MPC-1304 on femoral blood flow. Moreover, diltiazem reduced a part of [3H]MPC-1304 binding in a competitive manner. In ex vivo binding assays with serum and aorta obtained after oral administration of the drug in spontaneously hypertensive rats, MPC-1304 inhibited [3H]nitrendipine binding to membrane preparations less potently than nifedipine. From these results, we conclude that MPC-1304 is a different type of dihydropyridine possessing the most potent vasodilating action of the representative dihydropyridines tested. Its activity cannot be explained solely by a slow interaction with voltage-dependent Ca2+ channels.
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Affiliation(s)
- K Miyoshi
- Pharmacology Research Laboratory, Taiho Pharmaceutical Co., Ltd., Tokushima, Japan
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Dong H, Lee CM, Huang WL, Peng SX. Cardiovascular effects of substituted tetrahydroisoquinolines in rats. Br J Pharmacol 1992; 107:262-8. [PMID: 1330162 PMCID: PMC1907609 DOI: 10.1111/j.1476-5381.1992.tb14496.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
1. A series of substituted tetrahydroisoquinolins derived from the cleavage products of tetrandrine were found to inhibit [3H]-nitrendipine binding to rat cerebral cortical membranes. Those compounds which displaced [3H]-nitrendipine binding were also able to inhibit high KCl-induced contraction of rat aorta in vitro. 2. There was a significant correlation between the ability of these tetrahydroisoquinolines to inhibit [3H]-nitrendipine binding and KCl-induced contraction (r = 0.99, P less than 0.001). 3. CPU-23 (1-(1-[(6-methoxy)-naphth-2-yl])-propyl-2-(1-piperidine)-acetyl- 6,7- dimethoxy-1,2,3,4-tetrahydroisoquinoline), one of the most potent compounds identified in this series, behaved as a simple competitive inhibitor at the [3H]-nitrendipine binding site and reduced the apparent affinity but not the maximal number of binding sites in saturation analysis. 4. In contrast to nifedipine which caused hypotension and tachycardia, CPU-23 induced both hypotension and bradycardia in a dose-dependent manner in pentobarbitone-anaesthetized Sprague-Dawley rats, spontaneously hypertensive and age-matched normotensive WKY rats. 5. It is suggested that CPU-23 may exert its cardiovascular effects via interaction with the dihydropyridine binding site on the L-type calcium channel.
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Affiliation(s)
- H Dong
- Chinese Medicinal Material Research Centre, Chinese University of Hong Kong, Shatin, N.T
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18
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Miwa K, Miyagi Y, Araie E, Sasayama S. Effects of diltiazem and verapamil on (+)-PN 200-110 binding kinetics in dog cardiac membranes. Eur J Pharmacol 1992; 214:127-32. [PMID: 1325351 DOI: 10.1016/0014-2999(92)90109-h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The effects of d-cis-diltiazem (diltiazem) and verapamil on 1,4-dihydropyridine binding to dog cardiac membranes were studied in competition, saturation and kinetic binding experiments with [3H](+)-PN200-110. Diltiazem increased [3H](+)-PN200-110 binding with an observed maximal effect at 50 microM, while verapamil decreased [3H](+)-PN200-110 binding in a dose-dependent manner. Scatchard analysis of saturation binding data revealed that diltiazem (50 microM) increased the maximal binding site density and verapamil (100 microM) increased the dissociation constant (KD) of [3H](+)-PN200-110 binding. The kinetic experiments demonstrated that diltiazem significantly reduced both the association and the dissociation rate of [3H](+)-PN200-110 binding, resulting in no significant change in the apparent KD. In contrast, verapamil accelerated dissociation and slowed down association of [3H](+)-PN200-110 binding. Diltiazem appears to alter both the number of [3H](+)-PN200-110 binding sites and the characteristics of [3H](+)-PN200-110 binding.
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Affiliation(s)
- K Miwa
- Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Japan
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19
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Nakayama K, Ishigai Y, Uchida H, Tanaka Y. Potentiation by endothelin-1 of 5-hydroxytryptamine-induced contraction in coronary artery of the pig. Br J Pharmacol 1991; 104:978-86. [PMID: 1810605 PMCID: PMC1908859 DOI: 10.1111/j.1476-5381.1991.tb12536.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
1. In order to elucidate the physiological and potential pathological roles of endothelin-1 (ET-1) in coronary artery contraction and relaxation, we undertook the present study to examine the action of ET-1 itself, and the combined effects of ET-1 with vasoconstrictor agonists such as acetylcholine (ACh), histamine, and 5-hydroxytryptamine (5-HT), all of which have been implicated in the genesis of coronary spasm. 2. Isometric tension and cytosolic Ca2+ concentration ([Ca2+]i) in a ring segment of porcine coronary artery loaded with fura-2 were measured simultaneously. 3. ET-1 contracted the artery in a concentration-dependent manner; and nisoldipine, a Ca2+ channel blocking drug of the 1,4-dihydropyridine type, antagonized the ET-1 action non-competitively. A radio-receptor binding assay also indicated the mutually exclusive binding of ET-1 and (+)-[3H]-PN200-110, a Ca2+ channel ligand, to the membrane fraction of porcine coronary artery. 4. ET-1 (10-100 pM) increased tension and [Ca2+]i in a parallel manner, while at higher concentrations (1-10 nM) it produced further contraction with a small increase in [Ca2+]i. 5. ET-1 (30-100 pM) selectively potentiated the 5-HT-induced contraction 1.5 to 2 times over the control without causing a significant increase in [Ca2+]i, which seems to be qualitatively similar to a tumour promoting phorbol ester, 12-deoxyphorbol 13-isobutylate (DPB). Bay K 8644 (10 nM), on the other hand, potentiated the contraction in response to practically all agonists used and affected a concomitant increase in [Ca2+]i.6. A Ca2+ channel blocking drug such as diltiazem abolished the increase in [Ca2+]i and partially attenuated the mechanical potentiation produced by a small amount of ET-1 in combination with 5-HT.7. The results suggest that ET-1 and 5-HT interact functionally at the cellular or subcellular level and modulate the Ca2 + sensitivity of the contractile elements through the possible activation of protein kinase C.
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Affiliation(s)
- K Nakayama
- Department of Pharmacology, University of Shizuoka, School of Pharmaceutical Sciences, Japan
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20
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Ikeda S, Oka J, Nagao T. Effects of four diltiazem stereoisomers on binding of d-cis-[3H]diltiazem and (+)-[3H]PN200-110 to rabbit T-tubule calcium channels. Eur J Pharmacol 1991; 208:199-205. [PMID: 1663043 DOI: 10.1016/0922-4106(91)90096-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Diltiazem, a benzothiazepine Ca2+ antagonist, has four stereoisomeric forms: d- and l-isomers of the cis and trans forms. All four isomers were shown to completely inhibit the binding of d-cis-[3H]diltiazem to rabbit T-tubule Ca2+ channels. The potency of the inhibition was in the order: d-cis greater than l-cis greater than d-trans = l-trans. The Hill slope for each inhibition was close to unity. The l-cis, d-trans and l-trans isomers had no effect on dissociation of the d-cis[3H]diltiazem-benzothiazepine receptor complex. These results indicate that all four isomers bind to benzothiazepine receptors. Furthermore, all of the isomers modulated (+)-[3H]PN200-110 binding. At 37 degrees C, only the d-cis isomer stimulated the binding, whereas the others showed inhibition. At 2 degrees C, all of them inhibited the binding. Both trans isomers exerted virtually the same, weak effects on the binding. It is concluded that the effects of diltiazem on radioligand binding to Ca2+ channels are highly stereospecific for the d-cis isomer.
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Affiliation(s)
- S Ikeda
- Department of Toxicology and Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan
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21
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Effect of bay K 8644, a calcium channel agonist, on dog cardiac muscarinic receptors. Arch Pharm Res 1991. [DOI: 10.1007/bf02876868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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22
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Positive heterotropic allosteric regulators of dihydropyridine binding increase the Ca2+ affinity of the L-type Ca2+ channel. Stereoselective reversal by the novel Ca2+ antagonist BM 20.1140. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)99087-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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23
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Navaratnam S, Khatter JC. Increased [3H]nitrendipine binding sites in rat heart during adult maturation and aging. Biochem Pharmacol 1991; 41:593-600. [PMID: 1847636 DOI: 10.1016/0006-2952(91)90632-f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
To study the effects of maturation and aging on calcium channels, we investigated the characteristics of binding of a radioligand, [3H]nitrendipine, to relatively pure sarcolemmal membranes from 2-, 12- and 24-month-old Sprague-Dawley rat hearts. Specific binding of [3H]nitrendipine was saturable, and the Scatchard analysis of the binding revealed a single class of binding sites. Binding of [3H]nitrendipine to the membrane of 12-month-old-rats was 50-75% greater than to the membrane of 2-month-old young adult rats with no further changes in binding during aging from 12 to 24 months. The maximum number of dihydropyridine binding sites (Bmax) was 70% higher in 12- and 24-month-old rat hearts (0.45 and 0.43 pmol/mg protein) than in 2-month-old rats (0.27 pmol/mg protein). The affinity for [3H]nitrendipine binding, on the other hand, was similar in all three age groups (KD values of 0.27, 0.31 and 0.29 nM in 2-, 12- and 24-month-old rats, respectively, at 25 degrees). Membranes of all three age groups showed a similar degree of enrichment in sarcolemmal marker enzymes, indicating that the difference in membrane purity was not a contributing factor to the observed increase in density. Furthermore, increased binding of [3H]nitrendipine to the membranes of older rat hearts was observed throughout the purification scheme. Since [3H]nitrendipine binding sites are considered to be specific sites for voltage-gated Ca2+ channels of the sarcolemma, it is concluded that the density of these channels in the myocardium increases during adult maturation and is maintained through senescence.
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Affiliation(s)
- S Navaratnam
- Department of Internal Medicine, University of Manitoba, Winnipeg, Canada
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24
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Nickerson PA, Yang F. Effect of nitrendipine on cardiac and renal lesions and arterial hypertrophy. Protective effect of a low dose of calcium antagonist in deoxycorticosterone-induced hypertensive rats. VIRCHOWS ARCHIV. B, CELL PATHOLOGY INCLUDING MOLECULAR PATHOLOGY 1990; 59:215-21. [PMID: 1980171 DOI: 10.1007/bf02899407] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A low dose of nitrendipine (1 mg/kg twice daily) ameliorated the percent incidence and severity of vascular lesions in the kidney and heart induced by deoxycorticosterone (DOC). Less protection was offered by administration of 1 mg/kg of the calcium antagonist once daily. A lower dose of the antagonist (0.5 mg/kg) administered twice daily produced almost no protection against myocardial scars, but the percent incidence and severity of renal tubular casts and glomerular changes were similar to those following injection of 1 mg/kg of the antagonist twice daily. DOC induced hypertrophy of the media in aorta, coronary artery and renal interlobular artery and renal arteriole. Neither 1 mg/kg once or twice daily nor 0.5 mg twice daily of calcium antagonist modified the hypertrophy of the arterial vasculature in the hypertensive DOC group. We conclude that a low dose of the calcium antagonist dissociates at least in part lesions but not hypertrophy from the increased systolic blood pressure, because the antagonist protects against vascular lesions induced by the hypertension. The antagonist likely acts on the endothelial cell of the vessels alone or combined with an effect on the vascular smooth muscle cells.
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Affiliation(s)
- P A Nickerson
- Department of Pathology, State University of New York, Buffalo 14214
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25
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Mironneau J, Sayet I, Rakotoarisoa L, Dacquet C, Mironneau C. Interactions of spironolactone with (+)-[3H]-isradipine and (-)-[3H]-desmethoxyverapamil binding sites in vascular smooth muscle. Br J Pharmacol 1990; 101:6-7. [PMID: 2149292 PMCID: PMC1917651 DOI: 10.1111/j.1476-5381.1990.tb12077.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Spironolactone partially inhibited the specific binding of (+)-[3H]-isradipine and (-)-[3H]-desmethoxyverapamil to vascular smooth muscle membranes. It is suggested that spironolactone interacts at a binding site of the calcium channel complex and allosterically modulates ligand binding at receptor sites in the channel.
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Affiliation(s)
- J Mironneau
- Laboratoire de Physiologie Cellulaire et Pharmacologie Moléculaire, INSERM Jeune Formation 88-13, Université de Bordeaux, France
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26
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Matlib MA. Relaxation of potassium chloride-induced contractions by amlodipine and its interaction with the 1,4-dihydropyridine-binding site in pig coronary artery. Am J Cardiol 1989; 64:51I-57I. [PMID: 2530885 DOI: 10.1016/0002-9149(89)90960-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Amlodipine is a light-insensitive and water soluble 1,4-dihydropyridine with prolonged vasodilatory action and plasma half-life. To determine whether the vasodilatory action of amlodipine is due to inhibition of voltage-dependent Ca2+ influx through the calcium channel, its effects on KCl-induced contraction of pig coronary artery rings and its interaction with the 1,4-dihydropyridine binding site in isolated sarcolemmal membranes were studied. The contractile function of artery rings was studied in an organ bath system, and the interaction with the 1,4-dihydropyridine binding site was studied in isolated sarcolemmal membranes of pig coronary artery using [3H](+)PN200-110 as a radioligand. Amlodipine, (+)PN200-110 and (-)PN200-110 inhibited KCl-induced contractions of arterial rings in a dose-dependent manner. The half-maximal inhibition (IC50) was observed at 0.46 +/- 0.02, 36 +/- 8 and 55 +/- 9 nM of (+)PN200-110, (-)PN200-110 and amlodipine, respectively. [3H](+)PN200-110 was found to bind to isolated sarcolemmal membranes with high affinity (KD = 0.04 nM, Bmax = 312 fmoles/mg protein) and stereospecifically, (+)PN200-110 (Ki = 0.05 nM) having about 130-fold higher affinity than (-)PN200-110 (Ki = 6.61 nM). Amlodipine also inhibited [3H](+)PN200-110 binding with high affinity (Ki = 4.41 nM). The inhibition was characterized by an increase in KD of binding of [3H](+)PN200-110 with very little effect on Bmax. The order of relative potency of inhibition of KCl-induced contraction was almost identical to the order of relative affinity for the 1,4-dihydropyridine binding site, as indicated by Ki.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M A Matlib
- Department of Pharmacology and Cell Biophysics, University of Cincinnati, College of Medicine, Ohio 45267-0575
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27
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Rossier JR, Cox JA, Niesor EJ, Bentzen CL. A new class of calcium entry blockers defined by 1,3-diphosphonates. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)84748-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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28
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Morel N, Godfraind T. Pharmacological properties of voltage-dependent calcium channels in functional microvessels isolated from rat brain. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1989; 340:442-51. [PMID: 2555723 DOI: 10.1007/bf00167047] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Voltage-operated calcium channels were studied in rat intracerebral microvessels. The contractile reactivity to KCl-depolarization was assessed by the measurement of internal diameter of superfused microvessels. Dihydropyridine receptor sites associated with calcium channels were identified and characterized using 3H(+)PN 200-110 [isopropyl-4-(2,1,3-benzodiazol-4-yl)-1,4-dihydro-2,6-dimethyl-5- -methoxycarbonyl-pyridine-3-carboxylate]. Depolarization induced by high-KCl solution produced a marked reduction of the internal diameter of cerebral microvessels which was associated with the appearance of rhythmic activity. The vessel contraction was reversible and abolished by nimodipine. Binding studies with 3H(+)PN 200-110 revealed the existence of a single class of specific, stereoselective and voltage-dependent binding sites which bound (+)PN 200-110 with a KD of 88 +/- 6.6 pmol l-1 at 37 degrees C in microvessels incubated in NaCl medium. When microvessels were incubated in KCl-medium, the apparent KD value was reduced to 35 +/- 2 pmol l-1. Bmax was not significantly changed. The effect of KCl was not related to concomitant changes in the Na concentration. The potency of various dihydropyridine derivatives in inhibiting 3H(+)PN 200-110 binding was in agreement with their pharmacological potency in smooth muscle preparations. The effect of PN 200-110 and of nimodipine was stereoselective. Ki values of PN 200-110 and of nimodipine were increased in depolarized preparations, while nifedipine's potency was unchanged. Verapamil was only a partial inhibitor of 3H(+)PN 200-110 binding. The effect of diltiazem was stereoselective: the (+)-cis isomer enhanced the binding and the (-)-cis isomer of diltiazem poorly inhibited the binding of PN 200-110. Results showed that isolated cerebral microvessels possess functional voltage-operated calcium channels, which contain potential-modulated receptors for dihydropyridine calcium entry blockers with characteristics similar to those described in other tissues.
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Affiliation(s)
- N Morel
- Laboratoire de Pharmacodynamie et de Pharmacologie, Université Catholique de Louvain, Bruxelles, Belgium
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29
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Palfreyman MG, Dudley MW, Cheng HC, Mir AK, Yamada S, Roeske WR, Obata T, Yamamura HI. Lactamimides: a novel chemical class of calcium antagonists with diltiazem-like properties. Biochem Pharmacol 1989; 38:2459-65. [PMID: 2757648 DOI: 10.1016/0006-2952(89)90089-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The effects of a series of lactamimides on [3H]d-cis-diltiazem binding to rat brain membranes, on [3H]nitrendipine binding to cardiac membranes, and on calcium-induced contractions in depolarized guinea pig taenia and ileum preparations were examined. Several of the lactamimides examined displaced [3H]d-cis-diltiazem binding and antagonized, in a competitive fashion, calcium-induced contractions. Over the series of lactamimides, there was a highly significant, positive linear correlation (r = 0.87, P less than 0.001) between their potency to displace [3H]d-cis-diltiazem and their potency to antagonize calcium-induced contractions in the depolarized taenia and ileum preparations. Of the lactamimides examined, MDL 16,582A [N-(2,2-diphenylpentyl)azacyclotridecan-2-imine. hydrochloride] had potency equivalent to d-cis-diltiazem with pA2 values of 7.27 and 7.38, respectively, against calcium-induced contractions in the guinea pig ileum. These lactamimides are a novel chemical class displaying diltiazem-like calcium antagonist properties.
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30
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Molecular tools of calcium channel studying: Synthesis and evaluation of biological activity of novel dihydropyridine calcium entry blockers. Bioorg Chem 1989. [DOI: 10.1016/0045-2068(89)90015-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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31
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Morón MA, Stevens CW, Yaksh TL. Diltiazem enhances and flunarizine inhibits nimodipine's antiseizure effects. Eur J Pharmacol 1989; 163:299-307. [PMID: 2721577 DOI: 10.1016/0014-2999(89)90199-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The dihydropyridine calcium channel antagonist, nimodipine has antiepileptic and anticonvulsive properties that are thought to be mediated through neuronal calcium channel blockade. The dihydropyridine binding site can be positively and negatively allosterically regulated by the benzothiazepines and the phenylalkylamines/piperazines, respectively. We investigated this binding interaction at the physiologic level by examining the effects of diltiazem (a benzothiazepine) and flunarizine (a piperazine) on the antiseizure activity of nimodipine. Seizures were induced with pentylenetetrazole in awake rats with chronically implanted EEG electrodes. Calcium channel antagonists were administered intracerebroventricularly 30 min after pentylenetetrazole at doses given at 15 min intervals. Diltiazem and flunarizine alone lacked antiseizure properties. The calculated ED50 values for nimodipine were: nimodipine alone = 135 micrograms; nimodipine + diltiazem (100 micrograms) = 67 micrograms. Nimodipine + flunarizine (10 micrograms) completely suppressed nimodipine's antiseizure activity. These findings may reflect the interaction observed among these agents at binding sites associated with the calcium channel and supports the idea that dihydropyridines mediate their antiseizure actions through neuronal calcium channel antagonism.
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Affiliation(s)
- M A Morón
- Department of Pharmacology, Mayo Clinic, Rochester, MN 55905
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32
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Imagawa J, Satoh K, Taira N. Coronary vasodilator and cardiac effects of NKY-722, a novel hydrophilic 1,4-dihydropyridine derivative, in the blood-perfused dog heart. Cardiovasc Drugs Ther 1989; 3:81-90. [PMID: 2487526 DOI: 10.1007/bf01881532] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The coronary vasodilator and cardiac effects of NKY-722, a novel hydrophilic 1,4-dihydropyridine derivative, were evaluated in isolated, blood-perfused sinoatrial (SA) node, atrioventricular (AV) node, and papillary muscle preparations of dogs. NKY-722 was administered intraarterially. NKY-722 increased coronary blood flow in all preparations. In SA node preparations, NKY-722 reduced sinus rate and produced atrial standstill in large doses. The dose that produced a 15% (nearly half-maximum) decrease in sinus rate was about six times the dose that doubled coronary blood flow. In AV node preparations, NKY-722 prolonged AV conduction time and produced second- or third-degree AV block in large doses only when administered into the artery supplying the AV node. The dose that produced a 15% (nearly half-maximum) increase in AV conduction time was about 3.5 times the dose that doubled coronary blood flow. In paced papillary muscle preparations, NKY-722 reduced the force of contraction. However, the dose that produced a 50% decrease in the force of contraction of the paced papillary muscle was about 100 times the dose that doubled coronary blood flow. In spontaneously beating papillary muscle preparations, NKY-722 failed to change the beating rate. The vasodilator effect of NKY-722 was of longer duration than the negative chronotropic, dromotropic, and inotropic effects. These results indicate that NKY-722 is highly vasoselective, and the cardiovascular profile of NKY-722 is essentially identical to that of currently available, lipophilic 1,4-dihydropyridine calcium antagonists.
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Affiliation(s)
- J Imagawa
- Department of Pharmacology, Tohoku University School of Medicine, Sendai, Japan
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33
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Muramatsu M, Fujita-Tominaga A, Tanaka M, Ishii Y, Aihara H. A new Ca-antagonist, CD-349, binding to the Ca-channel of rat myocardium and brain and hog coronary artery. JAPANESE JOURNAL OF PHARMACOLOGY 1988; 48:453-62. [PMID: 2854176 DOI: 10.1254/jjp.48.453] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The binding to a Ca-channel of a novel 1,4-dihydropyridine (DHP) Ca-antagonist, 2-nitratopropyl 3-nitratopropyl 2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate (CD-349), was studied in rat myocardium and brain and hog coronary artery, and the binding was compared with that of other DHPs. In rat myocardium, the binding reaction of [3H]CD-349 was faster than that of nitrendipine (NTD). The association rate constant of [3H]CD-349 was about 10 times higher than that of [3H]NTD. The dissociation rate was also higher than that of [3H]NTD. Scatchard plot analysis of [3H]CD-349 binding showed one high affinity site for CD-349. The dissociation constant (Kd) and maximum number of binding sites (Bmax) were 333 pM and 286 fmoles/mg protein. They were almost the same as those for [3H]NTD. [3H]CD-349 and [3H]NTD bindings were dose dependently inhibited by 1,4-DHPs: nifedipine, nimodipine, nicardipine and CD-349. The order of the inhibitory potency of these drugs was CD-349 greater than nicardipine greater than nimodipine greater than nifedipine, when [3H]CD-349 and [3H]NTD were used as the ligands. Similar results were obtained for rat brain and hog coronary artery. [3H]CD-349 binding was not changed by alpha- or beta-adrenergic, cholinergic, histaminergic or serotonergic agents in rat myocardium. From these results, it is suggested that CD-349 binds to the Ca-channel reversibly with high affinity due to its high association rate for the site.
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Affiliation(s)
- M Muramatsu
- Research Center, Taisho Pharmaceutical Co., Ltd., Saitama, Japan
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34
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Higo K, Saito H, Matsuki N. Characteristics of [3H]nimodipine binding to sarcolemmal membranes from rat vas deferens and its regulation by guanine nucleotide. JAPANESE JOURNAL OF PHARMACOLOGY 1988; 48:213-21. [PMID: 2850380 DOI: 10.1254/jjp.48.213] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The binding properties of a 1,4-dihydropyridine (DHP) calcium entry blocker, [3H]nimodipine, to a microsomal fraction from rat vas deferens was characterized. The specific binding was saturable, rapid and reversible. Scatchard analysis of the binding revealed a single binding site, and the dissociation constant and the maximum number of binding sites were 0.31 +/- 0.02 nM and 97.0 +/- 7.19 fmol/mg protein, respectively. Both the Kd value obtained from the kinetic study and the IC50 value from relaxation of the K+-depolarized organ were approximately 0.4 nM, indicating that the binding site is closely related to the functional Ca2+ channel. The specific [3H]nimodipine binding was displaced by DHP derivatives at low concentration and by verapamil at high concentration, but diltiazem had no effect on the binding. Calcium chelating agents decreased the [3H]nimodipine binding which was restored by adding Ca2+. 5'-Guanylylimidodiphosphate caused a rightward shift of the displacement curve for Bay K 8644 but not for nimodipine, suggesting the involvement of guanine nucleotide binding protein in the signal transduction between the DHP binding site and the Ca2+ channel.
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Affiliation(s)
- K Higo
- Department of Chemical Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan
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35
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Yamada S, Harada Y, Nakayama K. Characterization of calcium channel antagonist binding sites labeled by [3H]nitrendipine in porcine coronary artery and aorta. Eur J Pharmacol 1988; 154:203-8. [PMID: 2852598 DOI: 10.1016/0014-2999(88)90099-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The receptor sites for dihydropyridine calcium channel antagonists in porcine coronary artery were characterized with [3H]nitrendipine (NTD), and were compared with those in the thoracic aorta. Specific [3H]NTD binding in the coronary artery and aorta was saturable, reversible and of high affinity. These sites showed a pharmacological specificity and stereoselectivity characteristic of the receptor sites for dihydropyridine calcium channel antagonists. The pharmacological potencies of nitrendipine, nifedipine, nisoldipine, (+)-PN 200-110 and (-)-PN 200-110 in the isolated porcine coronary artery correlated well with their potencies in competing for [3H]NTD binding sites. The Hill coefficients for the competition curves for these antagonists in the porcine coronary artery and aorta were close to one. Verapamil partially inhibited specific [3H]NTD binding in both tissues. The [3H]NTD binding was increased by Mg2+ and Ca2+ but was markedly reduced by EDTA. Thus, the present study has shown that [3H]NTD selectively labels the pharmacologically relevant dihydropyridine receptors in the porcine coronary artery and that there is no significant difference between the binding characteristics of the receptor sites in the coronary artery and aorta of pigs.
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Affiliation(s)
- S Yamada
- Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Japan
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36
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Hosey MM, Lazdunski M. Calcium channels: molecular pharmacology, structure and regulation. J Membr Biol 1988; 104:81-105. [PMID: 2903935 DOI: 10.1007/bf01870922] [Citation(s) in RCA: 299] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- M M Hosey
- Department of Biological Chemistry and Structure, Chicago Medical School, Illinois 60064
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37
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Dudkin SM, Gnedoj SN, Chernyuk NN, Soldatov NM. 1,4-Dihydropyridine receptor associated with Ca2+ channels in human embryonic fibroblasts. FEBS Lett 1988; 233:352-4. [PMID: 2454846 DOI: 10.1016/0014-5793(88)80458-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
By using the radioactively labeled 1,4-dihydropyridine (DHP) probe, [3H]PMD, we have demonstrated that cultured human embryonic fibroblasts grown at a low density in Eagle's medium supplemented with serum contain a single class of non-interacting DHP binding sites (Bmax, 1.2 +/- 0.3 pmol/10(6) cells; Kd, 3.9 nM). After inhibition of the DHP receptor biosynthesis by cycloheximide, the number of [3H]PMD binding sites is reduced with a half-time of 12 h, which implies a turnover rate of 30,000 +/- 7500 receptors/h per cell. With progression to confluency, the Bmax value decreased up to 0.28 +/- 0.08 pmol/10(6) cells without significant change in Kd value. When cells were grown at a low density in serum-free conditions, the number of [3H]PMD binding sites gradually increased 1.9-fold within 3 days. Addition of serum reversed this effect with the same time course. These results imply that the DHP-sensitive Ca2+ channels are involved in the control of the proliferation of human embryonic fibroblasts.
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Affiliation(s)
- S M Dudkin
- Institute of Biomedical Technology, USSR Ministry of Public Health, Moscow
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38
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Toyosaki N, Toyo-oka T, Natsume T, Katsuki T, Tateishi T, Yaginuma T, Hosoda S. Combination therapy with diltiazem and nifedipine in patients with effort angina pectoris. Circulation 1988; 77:1370-5. [PMID: 3286041 DOI: 10.1161/01.cir.77.6.1370] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The antianginal effects of diltiazem and nifedipine alone and in combination were evaluated in a double-blind, randomized, placebo-controlled trial in 11 patients (nine men and two women, 57 +/- 8 years old) with stable effort angina. Each patient received placebo, 30 mg of diltiazem, 10 mg of nifedipine, and 30 mg of diltiazem plus 10 mg of nifedipine four times daily for 1 week each. Antianginal efficacy was assessed by means of a treadmill exercise test. The exercise tolerance time was significantly prolonged from 235.1 +/- 52 (placebo period) to 342.2 +/- 101 sec by diltiazem (p less than .01) and to 325.6 +/- 73 sec by nifedipine (p less than .01). The drug combination further prolonged exercise time to 451.1 +/- 103 sec, which was significantly longer than the interval attained with either diltiazem (p less than .01) or nifedipine (p less than .01) alone. The plasma concentration of diltiazem was unaffected by the addition of nifedipine, whereas the plasma nifedipine concentration was significantly increased from 34.8 +/- 11 to 106.4 +/- 37 ng/ml (p less than .001) by the concomitant administration of diltiazem. These data suggest that exercise tolerance in patients with effort angina is increased by the concomitant administration of diltiazem and nifedipine associated with an increase in the nifedipine plasma concentration.
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Affiliation(s)
- N Toyosaki
- Department of Cardiology, Jichi Medical School, Tochigi, Japan
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39
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Soldatov NM. Purification and characterization of dihydropyridine receptor from rabbit skeletal muscle. EUROPEAN JOURNAL OF BIOCHEMISTRY 1988; 173:327-38. [PMID: 2834206 DOI: 10.1111/j.1432-1033.1988.tb14002.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Digitonin and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propane sulfonate (Chapso) were used to solubilize the receptor of dihydropyridine calcium antagonists from the transverse tubule membranes of rabbit skeletal muscle. The receptor retained the ability for selective adsorption from either detergent extract by dihydropyridine-Sepharose. Incubation of the affinity resin with nitrendipine resulted in the elution of the receptor protein composed of two main polypeptides with molecular masses of 160 kDa and 53 kDa, as shown by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Only these two subunits were found in the receptor preparation purified to a specific dihydropyridine-binding activity of 2500-2800 pmol/mg protein (60-70% purity) from digitonin-solubilized membranes by a combination of wheat-germ-agglutinin--Sepharose, anion-exchange and dihydropyridine-Sepharose chromatography steps. The individual subunits were isolated in dodecyl-sulfate-denatured form from the preparation of the receptor, enriched by a two-step large-scale procedure applied to Chapso-solubilized membranes. The 160-kDa subunit slowly changed its apparent molecular mass to 125 kDa upon disulfide bond reduction without formation of novel peptides. This finding implies that 160-kDa subunit is cross-linked by intramolecular S-S bridge(s). Chemical deglycosylation with trifluoromethanesulfonic acid showed that the carbohydrate content of large and small subunits accounted for 7.5% and 6.6% by mass, respectively. The dihydropyridine receptor subunits are glycosylated through N-glycoside bonds only. In their ratio of polar to hydrophobic amino acid residues in the amino acid composition of the receptor subunits, these polypeptides behave rather as peripheral proteins. It is suggested that the main portion of polypeptide chains is located outside the membrane in contact with solvent.
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Affiliation(s)
- N M Soldatov
- Institute of Biomedical Technology, USSR Ministry of Public Health, Moscow, USSR
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40
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Wagner JA, Guggino SE, Reynolds IJ, Snowman AM, Biswas A, Olivera BM, Snyder SH. Calcium antagonist receptors. Clinical and physiological relevance. Ann N Y Acad Sci 1988; 522:116-33. [PMID: 2454047 DOI: 10.1111/j.1749-6632.1988.tb33349.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- J A Wagner
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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41
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Interaction of tetrandrine with slowly inactivating calcium channels. Characterization of calcium channel modulation by an alkaloid of Chinese medicinal herb origin. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)69196-3] [Citation(s) in RCA: 120] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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42
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Marin J. Vascular effects of calcium antagonists. Uses in some cerebrovascular disorders. GENERAL PHARMACOLOGY 1988; 19:295-306. [PMID: 2458295 DOI: 10.1016/0306-3623(88)90020-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
1. Smooth muscle contraction is related to the intracellular free Ca2+ concentration. 2. Potential dependent Ca2+ channels (PDCs) are generally more sensitive to Ca2+-antagonists (CAts) than receptor-operated Ca2+ channels (ROCs). However, there exists a wide variation in the sensitivity of ROCs and CAts, which largely depends on the vessel studied. 3. Cerebral and coronary arteries seem to be very sensitive to CAts. 4. New dihydropyridines possess selectivity for the cerebrovascular bed. 5. The vasospasm subsequent to subarachnoid hemorrhage appears to be sensitive to CAts. 6. CAts prevent or reduce the neurologic alterations elicited by cerebral ischemia, and some of them induce beneficial effects in the prophylaxis of migraine.
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Affiliation(s)
- J Marin
- Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma, Madrid, Spain
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43
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ISHII K, KANO T, ANDO J. Sex Differences in [3H]Nitrendipine Binding and Effects of Sex Steroid Hormones in Rat Cardiac and Cerebral Membranes. ACTA ACUST UNITED AC 1988. [DOI: 10.1016/s0021-5198(19)43326-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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44
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Affiliation(s)
- I J Reynolds
- Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637
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45
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Brush KL, Perez M, Hawkes MJ, Pratt DR, Hamilton SL. Low affinity binding sites for 1,4-dihydropyridines in mitochondria and in guinea pig ventricular membranes. Biochem Pharmacol 1987; 36:4153-61. [PMID: 2825717 DOI: 10.1016/0006-2952(87)90574-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In this paper, we describe the occurrence of both high and low affinity sites for dihydropyridines in crude membrane preparations from guinea pig ventricular tissue. The physiological significance of the low affinity site (apparent dissociation constant = 76 +/- 9 nM) is not currently known; it has, however, a binding capacity which was 300-1000 times that of the high affinity site and was resistant to heat denaturation. The magnitude of the binding to the low affinity site was affected by both the ionic strength of the medium and by the presence of divalent ions. Both unlabeled nitrendipine and nimodipine inhibited [3H]nitrendipine binding at both sites, but verapamil and diltiazem only affected binding at the high affinity site. We also characterized, both kinetically and by equilibrium binding, a low affinity, heat-stable nitrendipine binding site in purified mitochondria. The Bmax for this site was also dependent on ionic strength. This suggests the possibility that the low affinity site in crude membranes is due to mitochondrial contaminants and hence not directly related to voltage-dependent calcium channels.
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Affiliation(s)
- K L Brush
- Department of Physiology and Molecular Biophysics, Baylor College of Medicine, Houston, TX 77030
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46
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Howlett SE, Gordon T. Calcium channels in normal and dystrophic hamster cardiac muscle. [3H]nitrendipine binding studies. Biochem Pharmacol 1987; 36:2653-9. [PMID: 2440447 DOI: 10.1016/0006-2952(87)90547-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Progressive cardiac cell necrosis in the dystrophic hamster may be related to intracellular calcium overload, particularly as necrosis is prevented by treatment with calcium channel antagonists. Calcium overload could arise as a consequence of an imbalance in calcium influx, efflux and/or sequestration. The possibility that increased numbers of calcium channels in myopathic cells leads to excessive calcium influx has been studied by assaying the number of [3H]nitrendipine [( 3H]NTP) binding sites in cardiac muscle preparations. Crude homogenate and partially-purified ventricular muscle preparations from 60-day-old normal and genetically dystrophic hamsters were compared in this study. The results of equilibrium binding studies showed that, in both crude and partially-purified membrane preparations, the affinity and the maximum number of [3H]NTP binding sites in normal muscle were not significantly different from those measured in dystrophic muscle. For the homogenate preparation, the KD values were 0.07 +/- 0.01 and 0.08 +/- 0.01 nM for normal and dystrophic tissues, respectively, and the Bmax values were 62 +/- 6 and 73 +/- 6 fmol/mg protein for normal and dystrophic preparations respectively. These data show that a simple increase in the number of [3H]NTP binding sites is unlikely to account for calcium overload in the cardiomyopathic hamster.
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47
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Nishimura J, Kanaide H, Nakamura M. Characteristics of adrenoceptors and [3H]nitrendipine receptors of porcine vascular smooth muscle: differences between coronary artery and aorta. Circ Res 1987; 60:837-44. [PMID: 3036396 DOI: 10.1161/01.res.60.6.837] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Characteristics of the bindings of [3H](-)dihydroalprenolol, [125I](-)iodocyanopindolol, [3H]prazosin, [3H]yohimbine, and [3H]nitrendipine to porcine coronary membranes were investigated and the results compared with studies of porcine aortic membranes. In the equilibrium binding study carried out in sarcolemma-enriched fractions, there were no major differences in the Kd values of these radioligands between coronary artery and aorta. However, the densities of beta-, alpha 1-, and alpha 2-adrenoceptors and [3H]nitrendipine receptors of coronary artery were 258, 12, 12, and 561 fmol/mg protein, respectively, while those of aorta were 37, 525, 1,000, and 215 fmol/mg protein. beta-Adrenergic agonists competed with [3H](-)dihydroalprenolol binding sites in coronary artery, the order of potency being (-)isoproterenol greater than (-)norepinephrine greater than (-)epinephrine greater than (+)isoproterenol. In case of aorta, the order was (-)isoproterenol greater than (-)epinephrine greater than (-)norepinephrine. The competition by (+/-)bisoprolol (beta 1-selective antagonist) and ICI 118,551 (beta 2-selective antagonist) for [125I](-)iodocyanopindolol binding sites in coronary artery resulted in nonlinear Hofstee plots (beta 1:beta 2 = 90%:10%). In case of aorta, linear Hofstee plots were obtained. From these results, we conclude that coronary beta-receptors in pigs are predominantly of beta 1-type, while those of aorta are of beta 2-type; regarding the relative population of adrenoceptors, coronary artery is beta-dominant (beta/alpha = 11), while aorta is alpha-dominant (beta/alpha = 0.02); compared with alpha-adrenoceptors, coronary artery has a greater number of [3H]nitrendipine binding sites (nitrendipine/alpha-adrenoceptor = 23) than aorta (nitrendipine/alpha-adrenoceptor = 0.14).
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48
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Cargnelli G, Padrini R, Piovan D, Moretto R, Bova S. Effects of SAS 1310, a new calcium antagonist, on isolated myocardial and smooth muscle preparations. Eur J Pharmacol 1987; 136:163-70. [PMID: 3595719 DOI: 10.1016/0014-2999(87)90708-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Some features of the effects of the diltiazem derivative SAS 1310 on in vitro myocardial and smooth muscle preparations were compared to those of the effects of diltiazem. Left atria, aortic strips and taenia coli of guinea-pigs were used. SAS 1310 induced a negative inotropic response of the left atria driven at 1 Hz similar to the response to diltiazem (IC50 values: SAS 1310 1.34 microM, diltiazem 0.8 microM). The inotropic effect of diltiazem (5 microM) was clearly rate-dependent whereas the reduction of left atria contractility induced by SAS 1310 (5 microM) was not modified by changes of the stimulation rate (the range of frequencies used was 0.5-2 Hz, with stepwise changes of 0.5 Hz). Diltiazem (0.1-0.5 microM) was more effective than SAS 1310 (0.1-5 microM) in inhibiting the contractile response to calcium of taenia coli depolarized by high K+ as well as in relaxing the aortic strips contracted by high K+ (IC50 SAS 1310 12.3 microM, diltiazem 0.41 microM). The response of aortic strips to norepinephrine (50 microM) in Ca2+-free medium was inhibited by SAS 1310 (50 microM) and was not affected by diltiazem (2 microM). The drug concentrations used were equiactive in inhibiting the high K+-induced contraction of the aortic strips. The different effects of diltiazem and its derivative on left atria contraction at different force-frequency ratios and on aortic strip contraction induced by norepinephrine in a Ca2+-free medium suggest that the actions of the two drugs differ qualitatively.
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49
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Golichowski AM, Tzeng DY. Enhancement of binding of the dihydropyridine calcium antagonist PN200-110 to human myometrial sarcolemma by the heterologous calcium antagonist diltiazem. Biochem Pharmacol 1987; 36:1003-9. [PMID: 2952124 DOI: 10.1016/0006-2952(87)90406-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Binding of the dihydropyridine calcium antagonist PN200-110 was studied in human myometrial membranes. PN200-110 bound reversibly and with high affinity to membrane fragments. The highest concentration of binding sites was found in the sarcolemma. The benzothiazepine calcium antagonist diltiazem stimulated PN200-110 binding by increasing the amount bound at equilibrium. Kinetic studies detected a fast and slow rate of dissociation in the presence of diltiazem.
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50
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Lüllmann H, Mohr K. High and concentration-proportional accumulation of [3H]-nitrendipine by intact cardiac tissue. Br J Pharmacol 1987; 90:567-74. [PMID: 3567462 PMCID: PMC1917193 DOI: 10.1111/j.1476-5381.1987.tb11207.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The binding of [3H]-nitrendipine to intact, electrically driven isolated left atria of guinea-pigs was investigated over the concentration range 10(-10) M to 3 X 10(-5) M. A high affinity binding site saturable in the nM range as found in ventricular homogenates could not be detected. Instead the accumulation of nitrendipine in intact atria was found to be proportional to the concentration from 10(-10) M to 10(-6) M; beyond 10(-6) M the binding started to become saturated. Nitrendipine was highly accumulated in atrial tissue. The cell:medium ratios amounted to about 120 in the range from 10(-10) M to 10(-6) M. The concentration-response curve for the negative inotropic action of nitrendipine yielded an ED50 of 3 X 10(-7) M, thus lying within the range of concentration-proportional accumulation. The reduction of the contractile force proceeded faster (t1/2 less than 10 min) than the uptake process t1/2 approximately 40 min) suggesting that it is the binding of nitrendipine into a superficial compartment, which interferes with the excitation-contraction coupling. The results suggest that the high concentration of nitrendipine present in hydrophobic cellular compartments such as the plasmalemma might be involved in its pharmacological action.
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