The Journal of Membrane Biology

, Volume 139, Issue 3, pp 191–201 | Cite as

Chemically modified cardiac Na+ channels and their sensitivity to antiarrhythmics: Is there a hidden drug receptor?

  • I. Benz
  • M. Kohlhardt


Elementary Na+ currents were recorded at 19°C in inside-out patches from cultured neonatal rat cardiocytes. In analyzing the sensitivity of chemically modified Na+ channels to several class 1 antiarrhythmic drugs, the hypothesis was tested that removal of Na+ inactivation may be accompanied by a distinct responsiveness to these drugs, open channel blockade.

Iodate-modified and trypsin-modified cardiac Na+ channels are noninactivating but strikingly differ from each other by their open state kinetics, a O1–O2 reaction (τopen(1) 1.4±0.3 msec; τopen(2) 5.4±1.1 msec; at −40 mV) in the former and a single open state (τopen 3.0±0.5 msec; at −40 mV) in the latter. Lidocaine (150 μmol/liter) like propafenone (10 μmol/liter), diprafenone (10 μmol/liter) and quinidine (20 μmol/liter) in cytoplasmic concentrations effective to depress NP o significantly can interact with both types of noninactivating Na+ channels to reduce the dwell time in the conducting configuration. lodate-modified Na+ channels became drug sensitive during the O2 state. At −40 mV, for example, lidocaine reduced τopen(2) to 62±5% of the control without detectable changes in τopen(1). No evidence could be obtained that these inhibitory molecules would flicker-block the open Na+ pore. Drug-induced shortening of the open state, thus, is indicative for a distinct mode of drug action, namely interference with the gating process. Lidocaine proved less effective to reduce τopen(2) when compared with the action of diprafenone. Both drugs apparently interacted with individual association rate constants, alidocaine was 0.64×106 mol−1 sec−1 and adiprafenone 13.6×106 mol−1 sec−1. Trypsin-modified Na+ channels also appear capable of discriminating among these antiarrhythmics, the ratio adiprafenone/alidocaine even exceeded the value in iodate-modified Na+ channels. Obviously, this antiarrhythmic drug interaction with chemically modified Na+ channels is receptor mediated: drug occupation of such a hypothetical hidden receptor that is not available in normal Na+ channels may facilitate the exit from the open state.

Key words

Single noninactivating Na+ channels Iodate Trypsin (−)-DPI 201-106 Drug-sensitive open state Channel-associated binding sites 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Alpert, L.A., Fozzard, H.A., Hanck, D.A., Makielski, J.C. 1989. Is there a second external lidocaine binding site on mammalian cardiac cells? Am. J. Physiol 257:H79-H84Google Scholar
  2. Baumgarten, C.M., Makielski, J.C., Fozzard, H.A. 1991. External site for local anesthetic block of cardiac Na+ channels. J. Mol. Cell Cardiol. 23:85–93Google Scholar
  3. Beck, W., Benz, I., Bessler, W., Jung, G., Kohlhardt, M. 1993. Responsiveness of cardiac Na+ channels to a site-directed antiserum against the cytosolic linker between domains III and IV and their sensitivity to other modifying agents. J. Membrane Biol. 134:231–239Google Scholar
  4. Benz, I., Kohlhardt, M. 1991. Responsiveness of cardiac Na+ channels to antiarrhythmic drugs: the role of inactivation. J. Membrane Biol. 122:267–278Google Scholar
  5. Benz, I., Kohlhardt, M. 1992. Differential response of DPI-modified cardiac Na+ channels to antiarrhythmic drugs: no flicker blockade by lidocaine. J. Membrane Biol. 126:257–263Google Scholar
  6. Brown, A.M., Lee, K.S., Powell, T. 1981. Sodium currents in single rat heart cells. J. Physiol. 318:479–500Google Scholar
  7. Cahalan, M.D. 1978. Local anesthetic block of sodium channels in normal and pronase-treated squid giant axons. Biophys. J. 23:285–311Google Scholar
  8. Cannon, S.C., Strittmatter, S.M. 1993. Functional expression of sodium channel mutations identified in families with periodic paralysis. Neuron 10:317–326Google Scholar
  9. Carmeliet, E., Nilius, B., Vereecke, J. 1989. Properties of the block of single Na+ channels in guinea-pig ventricular myocytes by the local anaesthetic Penticainide. J. Physiol. 409:241–262Google Scholar
  10. Clarkson, C.W. 1990. Modification of Na+ channel inactivation by a-chymotrypsin in single cardiac myocytes. Pfluegers Arch. 417:48–57Google Scholar
  11. Colquhoun, D., Sigworth, F.J. 1983. Fitting and statistical analysis of single channel records. in: Single Channel Recordings. B. Sakmann and E. Neher, editors, pp 191–264. Plenum, New YorkGoogle Scholar
  12. Gonoi, T., Hille, B. 1987. Gating of Na channels. Inactivation modifiers discriminate among models. J. Gen. Physiol. 89:253–274Google Scholar
  13. Gorin, G., Godwin, W.E. 1966. The reaction of iodate with cysteine and with insulin. Biochem. Biophys. Res. Commun. 25:227–232Google Scholar
  14. Grant, A.O., Dietz, M.A., Gilliam, F.R., Starmer, C.F. 1989. Blockade of cardiac sodium channels by lidocaine. Single channel analysis. Circ. Res. 65:1247–1262Google Scholar
  15. Gruber, R., Vereecke, J., Carmeliet, E. 1991. Dual effect of the local anaesthetic penticainide on the Na+ current of guinea-pig ventricular myocytes. J. Physiol. 435:65–81Google Scholar
  16. Hamill, O.P., Marty, A., Neher, E., Sakmann, B., Sigworth, F.J. 1981. Improved patch-clamp techniques for high resolution current recordings from cells and cell-free membrane patches. Pfluegers Arch. 391:85–100Google Scholar
  17. Hille, B. 1977. Local anesthetics: Hydrophilic and hydrophobic pathways for the drug-receptor reaction. J. Gen. Physiol. 69:497–515Google Scholar
  18. Hondeghem, L.M., Katzung, B.G. 1977. Time-and voltage-dependent interactions of antiarrhythmic drugs with cardiac sodium channels. Biochim. Biophys. Acta 472:373–398Google Scholar
  19. Huang, L.-Y.M., Ehrenstein, G. 1981. Local anesthetics QX-572 and benzocaine act at separate sites on the batrachotoxin-activated Na+ channel. J. Gen. Physiol. 77:137–153Google Scholar
  20. Isom, L.L., deGongh, K.S., Patton, D.E., Reber, B.F.X., Offord, J., Charbonneau, H., Walch, K., Goldin, A.L., Catterall, W.A. 1992. Primary structure and functional expression of the β1 subunit of the rat brain sodium channel. Science 256:839–942Google Scholar
  21. Khodorov, B., Shishkova, L., Peganov, E., Revenko, S. 1976. Inhibition of Na+ currents in the frog Ranvier node treated with local anesthetics: role of slow Na+ inactivation. Biochim. Biophys. Acta 433:409–435Google Scholar
  22. Kohlhardt, M., Fichtner, H. 1988. Block of single cardiac Na+ channels by antiarrhythmic drugs: The effect of amiodarone, propafenone and diprafenone. J. Membrane Biol. 102:105–119Google Scholar
  23. Kohlhardt, M., Fichtner, H., Fröbe, U. 1988. Differences in open state of NBA-modified cardiac Na+ channels. Eur. Biophys. J. 15:189–292Google Scholar
  24. Kohlhardt, M., Fichtner, H., Fröbe, U. 1989. Gating in iodate-modified single cardiac Na+ channels. J. Membrane Biol. 112:67–78Google Scholar
  25. Kohlhardt, M., Fichtner, H., Fröbe, U., Herzig, J.W. 1989. On the mechanism of drug-induced blockade of Na+ currents: Interaction of antiarrhythmic compounds with DPI-modified single cardiac Na+ channels. Circ. Res. 64:867–881Google Scholar
  26. Kohlhardt, M., Fröbe, U., Herzig, J.W. 1986. Modification of single cardiac Na+ channels by DPI 201–106. J. Membrane Biol. 89:163–172Google Scholar
  27. Kohlhardt, M., Seifert, C. 1983. Tonic and phasic INa blockade by antiarrhythmics. Different properties of drug binding to fast sodium channels as judged from 200–1 studies with propafenone and derivatives in mammalian ventricular myocardium. Pfluegers Arch. 396:199–209Google Scholar
  28. Kohlhardt, M., Seifert, S. 1985. Properties of 200–2 block of INa-mediated action potentials during combined application of antiarrhythmic drugs in cardiac muscle. Naunyn-Schmiedeberg's Arch. Pharmacol. 330:235–244Google Scholar
  29. Koumi, S., Sato, R., Hayakawa, H., Okumura, H. 1991. Quinidine blocks cardiac sodium current after removal of the fast inactivation process with chloramine-T. J. Mol. Cell Cardiol. 23:427–438Google Scholar
  30. Mrose, H., Ritchie, J.M. 1978. Local anesthetics: Do benzocaine and lidocaine act at the same single site? J. Gen. Physiol. 71:223–225Google Scholar
  31. Nagy, K. 1988. Mechanism of inactivation of single sodium channels after modifications by chloramine-T, sea anemona toxin and scorpion toxin. J. Membrane Biol. 106:29–40Google Scholar
  32. Nilius, B., Vereecke, J., Carmeliet, E. 1989. Properties of the bursting Na+ channel in the presence of DPI 201–106 in guinea-pig ventricular myocytes. Pfluegers Arch. 413:234–241Google Scholar
  33. Quandt, F.N. 1987. Burst kinetics of sodium channels with lack fast inactivation in mouse neuroblastoma cells. J. Physiol. 392:563–585Google Scholar
  34. Ragsdale, D.S., Scheuer, T., Catterall, W.A. 1991. Frequency and voltage-dependent inhibition of type IIA Na+ channels, expressed in a mammalian cell line, by local anesthetic, antiarrhythmic, and anticonvulsant drugs. Mol. Pharmacol. 40:756–765Google Scholar
  35. Romey, G., Quast, U., Pauron, D., Frelin, C., Renaud, J.F., Lazdunski, M. 1987. Na+ channels as sites of action of the cardiotonic agent DPI 201–106 with agonist and antagonist enantiomers. Proc. Natl. Acad. Sci. USA 84:896–900Google Scholar
  36. Satin, J., Kyle, J.W., Chen, M., Rogart, R., Fozzard, H.A. 1992. The cloned cardiac Na+ channel α-subunit expressed in Xenopus oocytes show gating and blocking properties of native channels. J. Membrane Biol. 130:11–22Google Scholar
  37. Schreibmayer, W., Tritthart, H.A., Schindler, H. 1989. The cardiac sodium channel shows a regular substrate pattern indicating synchronized activity of several ion pathways instead of one. Biochim. Biophys. Acta 986:172–186Google Scholar
  38. Starmer, C.F., Grant, A.O. 1985. Phasic ion channel blockade. A kinetic model of parameter estimation procedure. Mol. Pharmacol. 28:348–356Google Scholar
  39. Starmer, C.F., Grant, A.O., Strauss, H.C. 1984. Mechanism of use-dependent block of sodium channels in excitable membranes by local anesthetics. Biophys. J. 46:15–27Google Scholar
  40. Stimmer, W., Conti, F., Suzuki, H., Wang, X., Noda, M., Yahagi, N., Kubo, H., Numa, S. 1989. Structural parts involved in activation and inactivation of the sodium channel. Nature 339:597–603Google Scholar
  41. Vassilev, P.M., Scheuer, T., Catterall, W.A. 1988. Identification of an intracellular peptide segment involved in sodium channel inactivation. Science 241:1658–1661Google Scholar
  42. Wang, G.K. 1988. Cocaine-induced closures of single batrachotoxin-activated Na+ channels in planar lipid bilayers. J. Gen. Physiol. 92:747–765Google Scholar
  43. Yamamoto, D., Yeh, J.S. 1984. Kinetics of 9-aminoacridine block of single Na+ channels. J. Gen. Physiol. 84:361–377Google Scholar
  44. Zilberter, Y.I., Motin, L.G. 1991. Existence of two fast inactivation states in cardiac Na+ channels confirmed by two-stage action of proteolytic enzymes. Biochim. Biophys. Acta 1068:77–80Google Scholar

Copyright information

© Springer-Verlag New York Inc. 1994

Authors and Affiliations

  • I. Benz
    • 1
  • M. Kohlhardt
    • 1
  1. 1.Physiological Institute of the University of FreiburgFreiburg/Br.Germany

Personalised recommendations