Characterization of transient outward K+ current and ultra-rapid delayed rectifier K+ current in isolated human atrial myocytes from patients with congestive heart failure.
Abstract
AIM: To study the properties of transient outward K+ current (Ito) and
ultra-rapid delayed rectifier K+ current (IKur) in isolated human atrial myocytes
from patients with congestive heart failure (CHF).
METHODS: Single cells were isolated from CHF patients with collagenase and
protease. Ito and IKur were recorded using whole cell patch-clamp technique.
RESULTS: The activation and inactivation of I(to) were voltage-dependent and
time-dependent. The half-activation and half-inactivation voltage were (15 +/-
12) mV and (-45 +/- 4) mV respectively. When membrane potential went up from -40
mV to +60 mV, the activation time constant means decreased from (6.9 +/- 2.3) ms
to (1.40 +/- 0.20) ms, while the inactivation time constant means decreased from
(69 +/- 17) ms to (21 +/- 14) ms. Otherwise, the mean reactivation time constants
was (125 +/- 65) ms when the membrane potential was held at -80 mV, but the
recovery was not complete during the interval observed. Ito showed less
frequency-dependent reduction at test frequency between 0.2-2 Hz. Compared with
Ito, the activation of IKur only showed voltage-dependence, without
time-dependence. Its mean current densities was (3.4 +/- 0.7) pA/pF when test
potential was +60 mV. The half activation voltage of IKur was (23 +/- 14) mV. No
clear frequency-dependence was observed at the same frequency range of Ito
either.
CONCLUSION: I(to) and IKur are important outward potassium channel currents in
isolated human atrial myocytes from CHF patients and they have different kinetic
properties.
Keywords:
ultra-rapid delayed rectifier K+ current (IKur) in isolated human atrial myocytes
from patients with congestive heart failure (CHF).
METHODS: Single cells were isolated from CHF patients with collagenase and
protease. Ito and IKur were recorded using whole cell patch-clamp technique.
RESULTS: The activation and inactivation of I(to) were voltage-dependent and
time-dependent. The half-activation and half-inactivation voltage were (15 +/-
12) mV and (-45 +/- 4) mV respectively. When membrane potential went up from -40
mV to +60 mV, the activation time constant means decreased from (6.9 +/- 2.3) ms
to (1.40 +/- 0.20) ms, while the inactivation time constant means decreased from
(69 +/- 17) ms to (21 +/- 14) ms. Otherwise, the mean reactivation time constants
was (125 +/- 65) ms when the membrane potential was held at -80 mV, but the
recovery was not complete during the interval observed. Ito showed less
frequency-dependent reduction at test frequency between 0.2-2 Hz. Compared with
Ito, the activation of IKur only showed voltage-dependence, without
time-dependence. Its mean current densities was (3.4 +/- 0.7) pA/pF when test
potential was +60 mV. The half activation voltage of IKur was (23 +/- 14) mV. No
clear frequency-dependence was observed at the same frequency range of Ito
either.
CONCLUSION: I(to) and IKur are important outward potassium channel currents in
isolated human atrial myocytes from CHF patients and they have different kinetic
properties.