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Ouabain-induced hypertension enhances left ventricular contractility in rats. Life Sci 2006; 79:1537-45. [PMID: 16716361 DOI: 10.1016/j.lfs.2006.04.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2006] [Revised: 04/17/2006] [Accepted: 04/26/2006] [Indexed: 11/23/2022]
Abstract
Chronic ouabain treatment produces hypertension acting on the central nervous system and at vascular levels. However, cardiac effects in this model of hypertension are still poorly understood. Hence, the effects of hypertension induced by chronic ouabain administration ( approximately 8 microg day(-1), s.c.) for 5 weeks on the cardiac function were studied in Wistar rats. Ouabain induces hypertension but not myocardial hypertrophy. Awake ouabain-treated rats present an increment of the left ventricular systolic pressure and of the maximum positive and negative dP/dt. Isolated papillary muscles from ouabain-treated rats present an increment in isometric force, and this effect was present even when inotropic interventions (external Ca(2+) increment and increased heart rate) were performed. However, the sarcoplasmic reticulum activity and the SERCA-2 protein expression did not change. On the other hand, the activity of myosin ATPase increased without changes in myosin heavy chain protein expression. In addition, the expression of alpha(1) and alpha(2) isoforms of Na(+), K(+)-ATPase also increased in the left ventricle from ouabain-hypertensive rats. The present results showed positive inotropic and lusitropic effects in hearts from awake ouabain-treated rats, which are associated with an increment of the isometric force development and of the activity of myosin ATPase and expression of catalytic subunits of the Na(+), K(+)-ATPase.
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Nasser MG, Makarim RA, Nassar CF, Shammas NW, Habbal MZ, Jurjus A. Prostacyclin-enhanced calcium sequestration by microsomes isolated from rat left ventricle. PHARMACOLOGICAL RESEARCH COMMUNICATIONS 1988; 20:485-97. [PMID: 3047753 DOI: 10.1016/s0031-6989(88)80076-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The objective of these experiments was to investigate the direct effect of prostacyclin on calcium binding and uptake by microsomal vesicles isolated from rat left ventricle. The protein content of the preparation was found to be 2.73 +/- 0.18 mg microsomal protein/g of left ventricular wet weight. Steady-state calcium binding and uptake by microsomal vesicles was reached at 6 minutes in control animals and 20 sec in prostacyclin-treated experiments. Prostacyclin increased steady-state calcium binding and uptake from a control of 52.48 +/- 4.16 up to 109.31 +/- 3.06 nmol/mg protein (p less than 0.05) and from 238.07 +/- 12.37 up to 314.85 +/- 1.23 nmol/mg protein (p less than 0.05) respectively. Doubling the concentration of prostacyclin from initial dose of 1.2 x 10(-8) M did not alter calcium binding and uptake further.
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Affiliation(s)
- M G Nasser
- Department of Physiology, Faculty of Medicine, American University of Beirut, Lebanon
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Alonso GL, Arrigó DM, Terradas SE, Nikonov JM, Nespral D, Palomba SE. Calcium uptake, calcium release and adenosinetriphosphatase activity in sarcoplasmic reticulum fragments deposited on millipore filters. BIOCHIMICA ET BIOPHYSICA ACTA 1977; 468:31-50. [PMID: 141943 DOI: 10.1016/0005-2736(77)90149-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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4
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Sack DW, Mathes P, Harrison CE. [The calcium metabolism of myocardial mitochondria and sarcoplasmic reticulum in experimental potassium deficiency (author's transl)]. Basic Res Cardiol 1976; 71:76-86. [PMID: 1259688 DOI: 10.1007/bf01907785] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Mechanical Parameters of the whole, Langendorff-perfused cat heart and of isolated right ventricular papillary muscles are depressed in chronic potassium deficiency. 45Ca binding of sarcoplasmic reticulum (SR) was found to be diminished and correlated with a reduced contractility of the perfused hearts. 45Ca uptake of sarcoplasmic reticulum isolated from potassium deficient hearts was also reduced. The mitrochondrial 45Ca binding and endogenous Ca concentration were increased and there was a positive correlation between these two parameters. The data suggest that a reduced SR Ca binding plays a role in the depression of myocardial contractility in chronic potassium deficiency. Increased mitochondrial 45Ca binding in the presence of reduced 45Ca binding and uptake of sarcoplasmic reticulum suggests the possibility that mitochondria are an additional myocardial calcium pool in chronic potassium deficiency.
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Greenspan AM, Morad M. Electromechanical studies on the inotropic effects of acetylstrophanthidin in ventricular muscle. J Physiol 1975; 253:357-84. [PMID: 1082501 PMCID: PMC1348510 DOI: 10.1113/jphysiol.1975.sp011194] [Citation(s) in RCA: 41] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Three phases in the inotropic response of acetyl strophanthidin (AcS) on the electromechnical activity of the frog ventricular myocardium were identified and studied using a single sucrose voltage-clamp technique and other conventional electrophysiological methods. 2. the positive inotropic response of the drug was accompanied by a shift in tension-voltage relation, so that more tension developed with every depolarization step above the mechanical threshold (-50mV). Only at higher drug concentrations or with long exposure times did the mechanical threshold shift to more negative membrane potentials (-60 to-70 mV). 3. In tetrodotoxin-treated muscles AcS produced marked potentiation of twitch tension and an appropriate shift in the tension-voltage relation. 4. the positive inotropic response of the drug was not related to the magnitude of the direction of the fast or slow Na current. 5. in tetrodotoxin-treated ventricular strips the direction or the magnitude of the secondary inward current (ICa or INa) were not related to the inotropic effect of AcS. 6. AcS shortens the action potential markedly during the later stages of its positive inotropic response. When Ca2+ is omitted from the bathing solution AcS not only fails to shorten the action potential, but often prolongs it. 7. The shortening of the action potential in the presence of AcS is accompanied by an increase in the "instantaneous" membrane conductance both at rest and during the time course of the plateau. 8. The decline in the positive inotropic response of the drug was accompanied by the shortening of the action potential. Electrical or chemical prolongation of the action potential restored the full positive inotropic response if the membrane had not depolarized. 9. Membrane depolarization and the development of diastolic tension always occurred at later stages of drug action. Elevation of [Mg+2]degrees to 5 or 10 mM prevented or suppressed the membrane depolarization and the diastolic tension. 10. KCl-induced contractures were potentiated throughout the duration of drug exposure. The tonic component of the contracture tension was markedly elevated especially at later stages of drug action. 11. The experimental evidence suggests that no unitary mechanism could account for multiple actions of acetyl strophanthidin. However, the contributions of the Na pump, the Ca+2 sequestering system, and the K-efflux system to the various stages of drug action are discussed.
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7
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The force-frequency relationship: A comparative study between warm- and cold-blooded animals. Pflugers Arch 1972. [DOI: 10.1007/bf00587448] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Carsten ME, Reedy MK. Cardiac sarcoplasmic reticulum: chemical and electron microscope studies of calcium accumulation. JOURNAL OF ULTRASTRUCTURE RESEARCH 1971; 35:554-74. [PMID: 4258963 DOI: 10.1016/s0022-5320(71)80011-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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9
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Sulakhe PV, Dhalia NS. Excitation-contraction coupling in heart. VII. Calcium accumulation in subcellular particles in congestive heart failure. J Clin Invest 1971; 50:1019-27. [PMID: 4324071 PMCID: PMC292024 DOI: 10.1172/jci106573] [Citation(s) in RCA: 78] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The ability of heavy microsomes and mitochondria, isolated from the control and failing hearts of genetically dystrophic hamsters (BIO 14.6 strain), to accumulate calcium was examined. The rate and extent of energy-linked calcium binding (in the absence of oxalate) by the heavy microsomes of the failing heart were markedly depressed. The calcium uptake (in the presence of 5 mM oxalate) by the heavy microsomes of the failing heart was similar to that of the control heart. On the other hand, both the rate and extent of energy-linked calcium binding (in the absence of Pi and succinate) and calcium uptake (in the presence of 4 mM Pi and 5 mM succinate) by mitochondria were greatly reduced in the failing heart in comparison to the control. No difference in the total adenosine triphosphatase activities (Ca(++)-Mg(++) stimulated) of heavy microsomes or mitochondria was observed between the control and failing hearts. These results indicate an abnormality of subcellular membranes of the failing heart to bind calcium and support the growing conviction concerning the defective "calcium pump" as a molecular abnormality associated with a moderate degree of congestive heart failure.
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11
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Sreter F, Ikemoto N, Gergely J. The effect of lyophilization and dithiothreitol on vesicles of skeletal and cardiac muscle sarcoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA 1970; 203:354-7. [PMID: 4245537 DOI: 10.1016/0005-2736(70)90154-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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12
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13
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Baird TJ, Binnion PF. Factors affecting the uptake of calcium by canine myocardial sarcoplasmic reticulum. Ir J Med Sci 1969; 8:585-93. [PMID: 5374227 DOI: 10.1007/bf02955471] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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14
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Dhalla NS. Excitation-contraction coupling in heart. I. Comparison of calcium uptake by the sarcoplasmic reticulum and mitochondria of the rat heart. ARCHIVES INTERNATIONALES DE PHYSIOLOGIE ET DE BIOCHIMIE 1969; 77:916-34. [PMID: 4190879 DOI: 10.3109/13813456909059804] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Abstract
Isolated vesicles of the sarcoplasmic reticulum are known to take up calcium when provided with magnesium adenosine triphosphate as an energy source. Preparations of high activity are obtained by keeping the vesicles in 5 millimolar dithiothreitol (a reagent that reduces disulfide groups), and these preparations retain activity for a week or longer. The highly active preparations lend themselves to a spectrophotometric method for following calcium uptake, and continuous uptake kinetics are readily obtained. Calcium uptake appears to follow Michaelis-Menten kinetics (K(m) = 8x10(-6); V(mas), = 7x10(-7) mole per second per milligram of protein). These preparations are also useful for studying the effects of inhibitors of uptake, such as quinine. When extrapolated to the intact muscle, the results from these isolated vesicles should give a better estimate than has been available of the actual rates of calcium uptake and of the physiological effect of inhibitors of uptake.
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Dransfeld H, Greeff K, Schorn A, Ting BT. Calcium uptake in mitochondria and vesicles of heart and skeletal muscle in presence of potassium, sodium, k-strophanthin and pentobarbital. Biochem Pharmacol 1969; 18:1335-45. [PMID: 5799107 DOI: 10.1016/0006-2952(69)90246-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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17
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Carsten ME. Role of calcium binding by sarcoplasmic reticulum in the contraction and relaxation of uterine smooth muscle. J Gen Physiol 1969; 53:414-26. [PMID: 4238459 PMCID: PMC2202867 DOI: 10.1085/jgp.53.4.414] [Citation(s) in RCA: 112] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The binding of calcium by isolated sarcoplasmic reticulum from cow uterus was studied. Sarcoplasmic reticulum was prepared by differential centrifugation. Three fractions were obtained: I, sedimented between 2,500-15,000 x g; II at 40,000 x g; and III, at 150,000 x g. Fraction II was further purified on a sucrose density gradient. All three fractions contained considerable amounts of intrinsic calcium, mostly in fraction I. Calcium binding in the presence of ATP(1) and Mg also was greatest in fraction I, followed by fraction II, with less in fraction III. Without ATP no calcium was taken up. 5 and 10 mM sodium azide partially inhibited calcium binding in fraction I, but not in fraction II, suggesting the presence of some mitochondria or mitochondrial fragments in fraction I. Calcium binding in fraction II was completely inhibited by 3 mM salyrgan; this fraction thus appears to be sarcoplasmic reticulum. ATPase activity was found in all three fractions, highest in fraction II. It is computed that calcium binding in fractions I and II, on the basis of a 50% yield of protein, is sufficient to elicit contraction by supplying calcium to the contractile proteins of the smooth muscle cell and to regulate relaxation and contraction.
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Entman ML, Cook JW, Bressler R. The influence of ouabain and alpha angelica lactone on calcium metabolism of dog cardiac microsomes. J Clin Invest 1969; 48:229-34. [PMID: 4236805 PMCID: PMC322214 DOI: 10.1172/jci105979] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The influence of ouabain and alpha angelica lactone on (45)calcium accumulation in cardiac microsomes was studied. Calcium binding (accumulation in the absence of excess oxalate or phosphate) was augmented by both ouabain and alpha angelica lactone in the presence of adenosine triphosphate (ATP) but unaffected in its absence. Calcium turnover (defined as the change in (45)Ca(++) bound to the microsomes after the specific activity is changed) was studied to determine if the augmented bound pool was freely exchangeable at equilibrium. Ouabain and alpha angelica lactone augmented calcium turnover in both the presence and absence of ATP. Calcium-stimulated ATPase was increased by both agents.It is proposed that these two unsaturated lactones, with known cardiotonic activity, may exert their effects by providing an increased contraction-dependent calcium pool to be released upon systolic depolarization.
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Scholz H. [Differences in contractural character of ventricular and atrial preparations from homoiotherm hearts]. Pflugers Arch 1969; 312:63-81. [PMID: 5388471 DOI: 10.1007/bf00588532] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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21
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Alonso G, Walser M. ATP splitting and calcium binding by brain microsomes measured with a rapid perfusion method. J Gen Physiol 1968; 52:111-35. [PMID: 5742826 PMCID: PMC2225800 DOI: 10.1085/jgp.52.1.111] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Rat brain microsomes, immobilized on a filter, were perfused with ATP-containing solutions in a device which made possible rapid change of perfusion media and frequent sampling of effluent. Inorganic phosphate production could be measured 10 times per sec. When ATP, sodium, or potassium was absent from the first perfusion medium and present in a second, and introduced without interrupting flow, phosphate output rose within a few tenths of a second. Inhibition by ouabain began within 0.3 sec but did not become maximal for at least 10 sec. Rapid binding of ouabain was minimal or absent, as was rapid release of ouabain on introducing potassium abruptly. Although the preparation bound some calcium reversibly, no measurable uptake of calcium occurred coincident with activation by ATP or by potassium, and no measurable release of calcium occurred coincident with the onset of ouabain inhibition. However, activation by sodium was consistently associated with simultaneous release (within < 1 sec) of calcium, averaging 46 pmole per mg of protein. Calcium release in response to sodium also occurred in the absence of ATP or in the presence of ouabain. At 0 degrees C sodium produced neither activation nor calcium release. The results are consistent with the possibility that sodium and calcium are competitively bound, even in the absence of ATP, to an active site on the enzyme distinct from the sites of potassium activation or glycoside inhibition.
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Graham JA, Lamb JF. The effect of adrenaline on the tension developed in contractures and twitches of the ventricle of the frog. J Physiol 1968; 197:479-509. [PMID: 5716855 PMCID: PMC1351811 DOI: 10.1113/jphysiol.1968.sp008571] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
1. The effect of adrenaline on contracture and twitch tension in frog's ventricle has been examined, using the superfused preparation.2. In 1 mM-Ca Ringer, contractures induced with excess KCl concentrations from 50 to 200 mM, are reduced by 1 x 10(-6) g/ml. adrenaline to an average of 0.62 of control values, in marked contrast to the well known positive inotropic effect of adrenaline on the heart twitch. This effect of adrenaline is directly dose dependent. Increasing [Ca](o) diminishes the effect of adrenaline on contracture tension, and on the twitch tension.3. Adrenaline has a significantly greater effect on the KCl contracture tension than noradrenaline or isoprenaline.4. In 1 mM-Ca Ringer, Na-free contractures are reduced to 0.72 of controls by 1 x 10(-6) g/ml. adrenaline. Adrenaline also significantly reduces tension in contractures induced by 50 c/s alternating current.5. The action of adrenaline on contracture tension is largely complete in 1-2 min at various rates of stimulation and calcium concentrations. A similar time course has been found for the effect of adrenaline on membrane potential.6. Pronethalol blocks the action of adrenaline on both twitch and contracture. The action on the contracture can also be blocked by ouabain (1 x 10(-5)M), and exposure of the tissue to K-free or Na-free Ringer solution.7. Adrenaline hyperpolarizes the membrane potential with a range of [K](o) from 0 to 200 mM. This effect is blocked by pronethalol and ouabain. After exposure to ouabain, adrenaline causes a significant decrease in the membrane potential. This may be due to an increase in the sodium permeability.8. At low values of the [Ca]/[Na](2) ratio, adrenaline takes a relatively constant number of beats for full action, but at high values of the ratio the development of full effect is largely time dependent.9. The time course of the effect on the twitch of changing from 0.5 to 2 mM-Ca Ringer has been studied at various rates of stimulation. The equilibration time has been found to depend on the heart rate.10. The effect on the contracture suggests that adrenaline decreases the calcium permeability. It is further suggested that the development of twitch tension is not due to direct Ca entry but is due to the release of Ca from a local store within or between the cells. The inotropic action of adrenaline is explained in terms of this store.
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Abstract
The concept that the positive inotropic effect of cardiac glycosides is dependent on the contractile state of the myocardium was tested. Isolated left atria of rabbits, when driven electrically at 15, 30, 60 and 120/min (at 30, 33, or 37°C), responded to ouabain (I µ/ml) in proportion to the number of contractions and not to the time of exposure or frequency of drive. Contraction-related effects were proportional to concentration of ouabain, acetylstrophanthidin, and digoxin. A contraction-related effect of ouabain was observed in anesthetized dogs with surgical A-V block, ventricular electrical drive and right ventricular contractile force recording. Quiescent rabbit atria exposed to ouabain for 30 min at 30°C and then washed in ouabain-free medium, showed minimal positive inotropic effect when stimulation was resumed. Toxic concentration of ouabain (5 µg/ml) in contact with quiescent atria for 30 min and then washed out, on resumption of stimulation had an immediate positive intropic (but no toxic) effect which diminished progressively, in contrast to the rapid development of toxic effects (ectopic contractions and contracture) in atria exposed to this dose of auabain during repetitive contractions. It is concluded that a major part of the positive intropic effect of cardiac glycosides is contraction dependent.
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