TY - JOUR
T1 - Role of Ca2+-activated Cl- current during proarrhythmic early after depolarizations in sheep and human ventricular myocytes
AU - Verkerk, A. O.
AU - Tan, H. L.
AU - Kirkels, J. H.
AU - Ravesloot, J. H.
PY - 2003
Y1 - 2003
N2 - OBJECTIVES: The proarrhythmic early afterdepolarizations (EADs) during phase-2 of the cardiac action potential (phase-2 EADs) are associated with secondary Ca2+-release of the sarcoplasmic reticulum. This makes it probable that the Ca2+-activated Cl- current [ICl(Ca)] is present during phase-2 EADs. Activation of ICl(Ca) during phase-2 of the action potential will result in an outwardly directed, repolarizing current and may thus be expected to prevent excessive depolarization of phase-2 EADs. The present study was designed to test this hypothesis. METHODS AND RESULTS: The contribution of ICl(Ca) during phase-2 EADs was studied in enzymatically isolated sheep and human ventricular myocytes using the patch-clamp methodology. EADs were induced by a combination of a low stimulus frequency (0.5 Hz) and exposure to 1 microm noradrenaline. In sheep myocytes, the ICl(Ca) blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS, 0.5 mm) abolished phase-1 repolarization of the action potential in all myocytes tested. This indicates that ICl(Ca) is present in all sheep myocytes. However, DIDS had no effect on phase-2 EAD characteristics. In human myocytes, DIDS neither affected phase-1 repolarization nor phase-2 EAD characteristics. CONCLUSION: In sheep ventricular myocytes, but not in human ventricular myocytes, ICl(Ca) contributes to phase-1 repolarization of the action potential. In both sheep and human myocytes, ICl(Ca) plays a limited role during phase-2 EADs
AB - OBJECTIVES: The proarrhythmic early afterdepolarizations (EADs) during phase-2 of the cardiac action potential (phase-2 EADs) are associated with secondary Ca2+-release of the sarcoplasmic reticulum. This makes it probable that the Ca2+-activated Cl- current [ICl(Ca)] is present during phase-2 EADs. Activation of ICl(Ca) during phase-2 of the action potential will result in an outwardly directed, repolarizing current and may thus be expected to prevent excessive depolarization of phase-2 EADs. The present study was designed to test this hypothesis. METHODS AND RESULTS: The contribution of ICl(Ca) during phase-2 EADs was studied in enzymatically isolated sheep and human ventricular myocytes using the patch-clamp methodology. EADs were induced by a combination of a low stimulus frequency (0.5 Hz) and exposure to 1 microm noradrenaline. In sheep myocytes, the ICl(Ca) blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS, 0.5 mm) abolished phase-1 repolarization of the action potential in all myocytes tested. This indicates that ICl(Ca) is present in all sheep myocytes. However, DIDS had no effect on phase-2 EAD characteristics. In human myocytes, DIDS neither affected phase-1 repolarization nor phase-2 EAD characteristics. CONCLUSION: In sheep ventricular myocytes, but not in human ventricular myocytes, ICl(Ca) contributes to phase-1 repolarization of the action potential. In both sheep and human myocytes, ICl(Ca) plays a limited role during phase-2 EADs
U2 - https://doi.org/10.1046/j.1365-201X.2003.01190.x
DO - https://doi.org/10.1046/j.1365-201X.2003.01190.x
M3 - Article
C2 - 14510777
SN - 0001-6772
VL - 179
SP - 143
EP - 148
JO - Acta Physiologica Scandinavica
JF - Acta Physiologica Scandinavica
IS - 2
ER -