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. 1987 Jun;91(2):315–319. doi: 10.1111/j.1476-5381.1987.tb10286.x

Electrophysiological effects of Ca antagonists, tetrodotoxin, [Ca]o and [Na]o on myocardium of hibernating chipmunks: possible involvement of Na-Ca exchange mechanism.

N Kondo
PMCID: PMC1853515  PMID: 3038236

Abstract

The electrophysiological performance of myocardium of hibernating chipmunks was investigated in the presence of Ca antagonists and tetrodotoxin, and the effects of high [Ca]o and low [Na]o were examined. The action potential of the preparations was characterized by the low amplitude of the plateau phase (APp). Ca antagonists, nifedipine (10(-6) M) and nitrendipine (2 X 10(-6) M), did not significantly inhibit this APp or the contraction. These nifedipine-insensitive electromechanical responses were completely abolished by an internal Ca release inhibitor, ryanodine. Both increasing [Ca]o and lowering [Na]o, by replacing Na by lithium or choline, also inhibited APp. Tetrodotoxin (10(-5) M) which markedly inhibited the initial rapid phase of the action potential slightly affected APp. These results suggest that the plateau potential of the present preparations is controlled by a process linked to Ca release from internal stores, most likely the Na-Ca exchange mechanism.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Attwell D., Cohen I., Eisner D., Ohba M., Ojeda C. The steady state TTX-sensitive ("window") sodium current in cardiac Purkinje fibres. Pflugers Arch. 1979 Mar 16;379(2):137–142. doi: 10.1007/BF00586939. [DOI] [PubMed] [Google Scholar]
  2. 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]
  3. Colquhoun D., Neher E., Reuter H., Stevens C. F. Inward current channels activated by intracellular Ca in cultured cardiac cells. Nature. 1981 Dec 24;294(5843):752–754. doi: 10.1038/294752a0. [DOI] [PubMed] [Google Scholar]
  4. Isenberg G., Ravens U. The effects of the Anemonia sulcata toxin (ATX II) on membrane currents of isolated mammalian myocytes. J Physiol. 1984 Dec;357:127–149. doi: 10.1113/jphysiol.1984.sp015493. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Kass R. S., Lederer W. J., Tsien R. W., Weingart R. Role of calcium ions in transient inward currents and aftercontractions induced by strophanthidin in cardiac Purkinje fibres. J Physiol. 1978 Aug;281:187–208. doi: 10.1113/jphysiol.1978.sp012416. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Kimura J., Noma A., Irisawa H. Na-Ca exchange current in mammalian heart cells. Nature. 1986 Feb 13;319(6054):596–597. doi: 10.1038/319596a0. [DOI] [PubMed] [Google Scholar]
  7. Kondo N. Excitation-contraction coupling in myocardium of nonhibernating and hibernating chipmunks: effects of isoprenaline, a high calcium medium, and ryanodine. Circ Res. 1986 Aug;59(2):221–228. doi: 10.1161/01.res.59.2.221. [DOI] [PubMed] [Google Scholar]
  8. Kondo N. Excitation-contraction coupling in the myocardium of hibernating chipmunks. Experientia. 1986 Dec 1;42(11-12):1220–1222. doi: 10.1007/BF01946394. [DOI] [PubMed] [Google Scholar]
  9. Kondo N., Shibata S. Calcium source for excitation-contraction coupling in myocardium of nonhibernating and hibernating chipmunks. Science. 1984 Aug 10;225(4662):641–643. doi: 10.1126/science.6740332. [DOI] [PubMed] [Google Scholar]
  10. Lederer W. J., Tsien R. W. Transient inward current underlying arrhythmogenic effects of cardiotonic steroids in Purkinje fibres. J Physiol. 1976 Dec;263(2):73–100. doi: 10.1113/jphysiol.1976.sp011622. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Marban E., Wier W. G. Ryanodine as a tool to determine the contributions of calcium entry and calcium release to the calcium transient and contraction of cardiac Purkinje fibers. Circ Res. 1985 Jan;56(1):133–138. doi: 10.1161/01.res.56.1.133. [DOI] [PubMed] [Google Scholar]
  12. Mechmann S., Pott L. Identification of Na-Ca exchange current in single cardiac myocytes. Nature. 1986 Feb 13;319(6054):597–599. doi: 10.1038/319597a0. [DOI] [PubMed] [Google Scholar]
  13. Mitchell M. R., Powell T., Terrar D. A., Twist V. W. Strontium, nifedipine and 4-aminopyridine modify the time course of the action potential in cells from rat ventricular muscle. Br J Pharmacol. 1984 Mar;81(3):551–556. doi: 10.1111/j.1476-5381.1984.tb10108.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Mitchell M. R., Powell T., Terrar D. A., Twist V. W. The effects of ryanodine, EGTA and low-sodium on action potentials in rat and guinea-pig ventricular myocytes: evidence for two inward currents during the plateau. Br J Pharmacol. 1984 Mar;81(3):543–550. doi: 10.1111/j.1476-5381.1984.tb10107.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Mullins L. J. The generation of electric currents in cardiac fibers by Na/Ca exchange. Am J Physiol. 1979 Mar;236(3):C103–C110. doi: 10.1152/ajpcell.1979.236.3.C103. [DOI] [PubMed] [Google Scholar]
  16. Narahashi T. Chemicals as tools in the study of excitable membranes. Physiol Rev. 1974 Oct;54(4):813–889. doi: 10.1152/physrev.1974.54.4.813. [DOI] [PubMed] [Google Scholar]
  17. Reeves J. P., Hale C. C. The stoichiometry of the cardiac sodium-calcium exchange system. J Biol Chem. 1984 Jun 25;259(12):7733–7739. [PubMed] [Google Scholar]
  18. Siegelbaum S. A., Tsien R. W. Calcium-activated transient outward current in calf cardiac Purkinje fibres. J Physiol. 1980 Feb;299:485–506. doi: 10.1113/jphysiol.1980.sp013138. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Sutko J. L., Kenyon J. L. Ryanodine modification of cardiac muscle responses to potassium-free solutions. Evidence for inhibition of sarcoplasmic reticulum calcium release. J Gen Physiol. 1983 Sep;82(3):385–404. doi: 10.1085/jgp.82.3.385. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Sutko J. L., Willerson J. T. Ryanodine alteration of the contractile state of rat ventricular myocardium. Comparison with dog, cat, and rabbit ventricular tissues. Circ Res. 1980 Mar;46(3):332–343. doi: 10.1161/01.res.46.3.332. [DOI] [PubMed] [Google Scholar]
  21. Wier W. G., Kort A. A., Stern M. D., Lakatta E. G., Marban E. Cellular calcium fluctuations in mammalian heart: direct evidence from noise analysis of aequorin signals in Purkinje fibers. Proc Natl Acad Sci U S A. 1983 Dec;80(23):7367–7371. doi: 10.1073/pnas.80.23.7367. [DOI] [PMC free article] [PubMed] [Google Scholar]

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