A fast transient outward monovalent current in rat saphenous myocytes passing through Ca2+ channels.
J Membr Biol
; 188(2): 87-95, 2002 Jul 15.
Article
de En
| MEDLINE
| ID: mdl-12172634
ABSTRACT
Transient outward currents in rat saphenous arterial myocytes were studied using the perforated configuration of the patch-clamp method. When myocytes were bathed in a Na-gluconate solution containing TEA to block large-conductance Ca2+-activated K+ (BK) currents, depolarizing pulses positive to +20 mV from a holding potential of -100 mV induced fast transient outward currents. The activation and inactivation time constants of the current were voltage dependent, and at +40 mV were 3.6 +/- 0.8 ms and 23.9 +/- 6.4 ms (n = 4), respectively. The steady-state inactivation of the transient outward current was steeply voltage dependent (z = 1.7), with 50% of the current inactivated at -55 mV. The current was insensitive to the A-type K+ channel blocker 4-AP (1-5 mM), and was modulated by external Ca, decreasing to approximately 0.85 of control values upon raising Ca2+ from 1 to 10 mM, and increasing approximately 3-fold upon lowering it to 0.1 mM. Transient outward currents were also recorded following replacement of internal K+ with either Na+ or Cs+, raising the possibility that the current was carried by monovalent ions passing through voltage-gated Ca2+ channels. This hypothesis was supported by the finding that the transient outward current had the same inactivation rate as the inward Ba2+ current, and that both currents were effectively blocked by the L-type Ca2+ channel blocker, nifedipine and enhanced by the agonist BAYK8644.
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Collection:
01-internacional
Base de données:
MEDLINE
Sujet principal:
Canaux calciques
/
Myocytes du muscle lisse
/
Potentiels de membrane
Type d'étude:
Diagnostic_studies
Limites:
Animals
Langue:
En
Journal:
J Membr Biol
Année:
2002
Type de document:
Article
Pays d'affiliation:
Italie