L-type calcium current in human ventricular myocytes at a physiological temperature from children with tetralogy of Fallot.
Cardiovasc Res
; 38(2): 424-32, 1998 May.
Article
en En
| MEDLINE
| ID: mdl-9709403
OBJECTIVE: The aim was to investigate the electrophysiological properties of the L-type calcium current (ICa,L) in ventricular myocytes at a physiological temperature (36-37 degrees C) isolated from children undergoing surgical repair of tetralogy of Fallot. METHODS: ICa,L was recorded with the patch-clamp technique in the single electrode whose-cell mode at a physiological calcium concentration (1.8 mmol/l) at 36-37 degrees C. RESULTS: Under these conditions, maximum current density averaged -5.80 +/- 0.45 pA/pF. ICa,L showed a bell-shaped current-voltage relationship: the current activated at -37.7 +/- 1.36 mV, peaked at +9.41 +/- 1.60 mV and reversed at +57.7 +/- 2.12 mV (n = 17). At +10 mV, time to peak of ICa,L was 5.23 +/- 0.46 ms. Membrane potentials for half-maximal steady-state activation and inactivation of ICa,L were -6.02 and -20.4 mV, respectively, the slope factors were 7.16 mV for steady-state activation and 6.49 mV for steady-state inactivation. ICa,L did not completely inactivate and showed a big window current between -45 and +40 mV. The inactivation of ICa,L showed a biexponential time course with a fast time constant ranging from 9.11 to 12.9 ms and a slow time constant ranging from 60.9 to 220 ms between -30 and +30 mV. Only the slow time constant showed a pronounced voltage dependency. The recovery from inactivation of ICa,L was biphasic with a fast time constant of 60.7 ms and a slow time constant of 619 ms. beta-Adrenergic stimulation with isoprenaline (1 mumol/l) increased the ICa,L density from -5.71 +/- 1.55 to -13.8 +/- 1.96 pA/pF (142%; P < 0.05) at +10 mV. CONCLUSIONS: The present study demonstrates that most of the electrophysiological properties of ICa,L in ventricular myocytes isolated from children with tetralogy of Fallot resemble those of adult ventricular cells. The existence of a big calcium window current could be involved in the occurrence of early afterdepolarizations which could lead to the high incidence of arrhythmias after surgical repair of tetralogy of Fallot.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Tetralogía de Fallot
/
Calcio
/
Miocardio
Límite:
Child, preschool
/
Humans
Idioma:
En
Revista:
Cardiovasc Res
Año:
1998
Tipo del documento:
Article
País de afiliación:
Austria
Pais de publicación:
Reino Unido