[Characterisation of transient outward potassium current (Ito1) in hypertrophied right ventricular myocytes from children with tetralogy of Fallot].

OBJECTIVE

To investigate whether a transient outward potassium current exists in children hypertrophy ventricular myocytes and to characterize its basic electrophysiological properties.

METHODS

Currents were recorded using whole-cell patch-clamp technique from enzymatically isolated ventricualr myocytes obtained from hearts of 10 patients aged 0.4-5 with tetralogy of Fallot (F4) ranging in age 0.4-5 years.

RESULTS

In almost all cells studied, a Ito1 could be recorded on depolarization to between -20(-)+60 mV under conditions in which Ca2+ current was blocked. The current density is 4.7 PA/PF +/- 0.6 PA/PF at 60 mV. Its inactivation time constants under tested potential 0, 20, 40, 60 mV were 123 ms +/- 6 ms, 131 ms +/- 11 ms, 122 ms +/- 6 ms, 122 ms +/- 6 ms Half-maximal activation occurred at 4.1 mV +/- 2.8 mV. Half-maximal steady-state inactivation was -41 mV +/- 4 mV. Recovery from inactivation was voltage-dependent and the time course was 83 ms +/- 4 ms.

CONCLUSION

A moderate Ca(2+)-independent transient outward K+ current is present in hypertrophied human ventricular myocytes from children with tetralogy of Fallot, its basic characteritics are similar to Ito1 observed in other species and human atria.