title: [The role of L-type Ca2+ current and reverse mode Na+ -Ca2+ exchange in activation of excitation-contraction coupling in guinea-pig ventricular myocytes].
abstract: OBJECTIVE
  To study and compare the excitation-contraction coupling triggered by L-type calcium current and by reverse-mode Na/Ca exchange during depolarizing steps in single guinea-pig ventricular myocytes.
  
  
  METHODS
  Whole-cell membrane-potential, membrane-current and cell-shortening data were simultaneously acquired during whole-cell voltage clamp protocols. Voltage clamp pulses elicited ICa(L) at + 10 mV, + 50 mV, + 100 mV and evoked contractions in myocytes superfused with Tyrode's solution at 35 degrees C.
  
  
  RESULTS
  The greater the inhibition of I(Ca(L)), the more likely contractions would be abolished at +10 mV test potential. There was a correlation between them. At potential positive to + 50 mV, contractions were partially suppressed by Nif 100 micromol/L or Nif 30 micromol/L plus Cd2+30 micromol/L. The residual contraction was significantly delayed in onset. At +100 mV test potential, contractions were delayed in onset compare to + 50 mV and resistant to Nif 100 micromol/L or Nif 30 micromol/L plus Cd2+30 micromol/L. The residual contraction was completely blocked by Ni2+ at + 50 mV and + 100 mV.
  
  
  CONCLUSIONS
  I(Ca(L)) is the major trigger for excitation-contraction coupling. Na/Ca exchange modulates excitation-contraction coupling as both reverse and forward mode.
authors.affiliation: Department of Cardiology, First Affiliated Hospital of Suzhou University, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Jiang
authors.forename: Xi-ping
authors.initials: XP
authors.lastname: Zhou
authors.forename: A J
authors.initials: AJ
authors.lastname: Pappano
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002460:Cell Line; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology*; D009200:Myocardial Contraction / Q000502:physiology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism* / Q000502:physiology*; D018408:Patch-Clamp Techniques; D012964:Sodium / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000502:physiology
chemical_list: D020746:Calcium Channels, L-Type; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D002118:Calcium