Abstract
The effects of digitoxin, 3 alpha-methyl-digitoxigenin-3 beta-monoglucoside (3 alpha-MDM), 3 alpha-methyl-digitoxigenin (3 alpha-MD), proscillaridin, 4, 5-methylene-procillaridin (4, 5-MP), and 3 beta-hydroxy-4, 5-methylene-A, B-trans-scillarenin (3 beta-HMTS) on force of contraction and on the transmembrane action potentials were examined in isolated papillary muscles of guinea-pigs. All derivatives exhibited the typical cardiac glycoside effects: i.e. they increased the force of contraction and shortened the action potential duration at 20% (plateau phase) and 90% of repolarization. With digitoxin, 3 beta-HMTS and 4, 5-MP a transient prolongation in action potential duration was observed at the lower concentrations. The action potential amplitude and the resting membrane potential were reduced consistently only with the higher concentrations used. The onset of the positive inotropic effects of 3 alpha-MDM, 3 alpha-MD and 3 beta-HMTS was more rapid than that of digitoxin and proscillaridin. The increment in contractile force reached a maximum well before the full shortening effect on the action potential duration had developed. The shortening of the action potential is thought to be responsible for the biphasic nature of the positive inotropic effect. With 3 alpha-MD and 3 alpha-MDM even toxic effects, e.g. increase in baseline tension, were completely reversible after washing in drug-free solution. The dose-response curves for the positive inotropism can only be compared reliably once the equilibrium of drug action has been established. This steady state is probably reflected by the development of the full shortening in action potential duration.
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Selected References
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- Akera T., Brody T. M. The role of Na+,K+-ATPase in the inotropic action of digitalis. Pharmacol Rev. 1977 Sep;29(3):187–220. [PubMed] [Google Scholar]
- Bassingthwaighte J. B., Fry C. H., McGuigan J. A. Relationship between internal calcium and outward current in mammalian ventricular muscle; a mechanism for the control of the action potential duration? J Physiol. 1976 Oct;262(1):15–37. doi: 10.1113/jphysiol.1976.sp011583. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bentfeld M., Lüllmann H., Peters T., Proppe D. Interdependence of ion transport and the action of quabain in heart muscle. Br J Pharmacol. 1977 Sep;61(1):19–27. doi: 10.1111/j.1476-5381.1977.tb09735.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Browning D. J., Guarnieri T., Strauss H. C. Ouabain effects on intracellular potassium activity and contractile force in cat papillary muscle. J Clin Invest. 1981 Oct;68(4):942–956. doi: 10.1172/JCI110349. [DOI] [PMC free article] [PubMed] [Google Scholar]
- DUDEL J., TRAUTWEIN W. Elektrophysiologiche Messungen zur Strophanthinwirkung am Herzmuskel. Naunyn Schmiedebergs Arch Exp Pathol Pharmakol. 1958;232(2):393–407. [PubMed] [Google Scholar]
- Daut J., Rüdel R. The electrogenic sodium pump in guinea-pig ventricular muscle: inhibition of pump current by cardiac glycosides. J Physiol. 1982 Sep;330:243–264. doi: 10.1113/jphysiol.1982.sp014339. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Godfraind T., Lesne M. The uptake of cardiac glycosides in relation to their actions in isolated cardiac muscle. Br J Pharmacol. 1972 Nov;46(3):488–497. doi: 10.1111/j.1476-5381.1972.tb08146.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Greenspan A. M., Morad M. Electromechanical studies on the inotropic effects of acetylstrophanthidin in ventricular muscle. J Physiol. 1975 Dec;253(2):357–384. doi: 10.1113/jphysiol.1975.sp011194. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lüllmann H., Mohr K. On the binding of a 3-alpha-methylated digitoxigenin-glucoside to ouabain receptors in heart muscle homogenate. Biochem Pharmacol. 1982 Aug 1;31(15):2489–2494. doi: 10.1016/0006-2952(82)90059-4. [DOI] [PubMed] [Google Scholar]
- Lüllmann H., Peters T. On the sarcolemmal site of action of cardiac glycosides. Recent Adv Stud Cardiac Struct Metab. 1976;9:311–328. [PubMed] [Google Scholar]
- Lüllmann H., Peters T. Plasmalemmal calcium in cardiac excitation-contraction coupling. Clin Exp Pharmacol Physiol. 1977 Jan-Feb;4(1):49–57. doi: 10.1111/j.1440-1681.1977.tb02377.x. [DOI] [PubMed] [Google Scholar]
- Lüllmann H., Peters T., Ravens U. Studies on the kinetics of (3H)-ouabain uptake and exchange in the isolated papillary muscle of the guinea-pig. Br J Pharmacol. 1975 Jan;53(1):99–107. doi: 10.1111/j.1476-5381.1975.tb07335.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lüllmann H., Ravens U. The time courses of the changes in contractile force and in transmembfane potentials induced by cardiac glycosides in guinea-pig papillary muscle. Br J Pharmacol. 1973 Nov;49(3):377–390. doi: 10.1111/j.1476-5381.1973.tb17248.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MUELLER P. OUABAIN EFFECTS ON CARDIAC CONTRACTION, ACTION POTENTIAL, AND CELLULAR POTASSIUM. Circ Res. 1965 Jul;17:46–56. doi: 10.1161/01.res.17.1.46. [DOI] [PubMed] [Google Scholar]
- Marban E., Tsien R. W. Enhancement of calcium current during digitalis inotropy in mammalian heart: positive feed-back regulation by intracellular calcium? J Physiol. 1982 Aug;329:589–614. doi: 10.1113/jphysiol.1982.sp014321. [DOI] [PMC free article] [PubMed] [Google Scholar]
- McDonald T. F., Nawrath H., Trautwein W. Membrane currents and tension in cat ventricular muscle treated with cardiac glycosides. Circ Res. 1975 Nov;37(5):674–682. doi: 10.1161/01.res.37.5.674. [DOI] [PubMed] [Google Scholar]
- Morad M., Orkand R. K. Excitation-concentration coupling in frog ventricle: evidence from voltage clamp studies. J Physiol. 1971 Dec;219(1):167–189. doi: 10.1113/jphysiol.1971.sp009656. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Morad M., Trautwein W. The effect of the duration of the action potential on contraction in the mammalian heart muscle. Pflugers Arch Gesamte Physiol Menschen Tiere. 1968;299(1):66–82. doi: 10.1007/BF00362542. [DOI] [PubMed] [Google Scholar]
- Noble D. Mechanism of action of therapeutic levels of cardiac glycosides. Cardiovasc Res. 1980 Sep;14(9):495–514. doi: 10.1093/cvr/14.9.495. [DOI] [PubMed] [Google Scholar]
- REPKE K., PORTIUS H. J. UBER DIE IDENTITAET DER IONENPUMPEN-ATPASE IN DER ZELLMEMBRAN DES HERZMUSKELS MIT EINEM DIGITALIS-REZEPTORENZYM. Experientia. 1963 Sep 15;19:452–458. doi: 10.1007/BF02150643. [DOI] [PubMed] [Google Scholar]
- Schwartz A., Lindenmayer G. E., Allen J. C. The sodium-potassium adenosine triphosphatase: pharmacological, physiological and biochemical aspects. Pharmacol Rev. 1975 Mar;27(01):3–134. [PubMed] [Google Scholar]
- Solaro R. J., Wise R. M., Shiner J. S., Briggs F. N. Calcium requirements for cardiac myofibrillar activation. Circ Res. 1974 Apr;34(4):525–530. doi: 10.1161/01.res.34.4.525. [DOI] [PubMed] [Google Scholar]
