Transient outward potassium current in rabbit atrium is depressed after short-time rapid atrial pacing but recovers after a longer pacing period.
In rabbit, after short-time rapid atrial pacing (RAP), atrial ion currents are reduced similarly as in human chronic atrial fibrillation (AF). Using the rabbit model, time-course of transient outward potassium current (I(to)) remodeling due to RAP was studied. RAP (600 bpm) was applied via an atrial lead for 0 (control), 24 and 120 h, n = 4 animals/group. Using patch clamp technique in whole-cell mode, current densities and biophysical properties were measured in isolated atrial myocytes. After 24 h of RAP, a reduction of peak I(to) (mean +/- SEM, test potential +50 mV, +37 degrees C) was observed (60.3 +/- 5.4 pA/pF (control, n = 20) vs. 28.0 +/- 2.5 pA/pF (24 h, n = 21)). Inactivation of I(to) was slower after 24 h, other biophysical properties were unaltered. However, I(to) recovered after 120 h: 51.7 +/- 4.5 pA/pF (n = 26, p = n.s. vs. control). Inactivation tended to also recover to initial values but was still different to control. Early I(to) remodeling due to RAP in rabbits seems to be more complex than previously thought: a time course of I(to) remodeling with swayings has to be considered when using the rabbit model of RAP in order to study early remodeling or rather its therapeutic manipulation.
Laszlo
R
R
Department of Cardiology, University of Tübingen, Otfried-Müller-Strasse 10, Tübingen, Germany. roman.laszlo@med.uni-tuebingen.de
Eick
C
C
Schwiebert
M
M
Schreiner
B
B
Weig
H J
HJ
Weretka
S
S
Schreieck
J
J
D000818:Animals; D016275:Atrial Function; D015220:Calcium Channels / Q000378:metabolism; D002304:Cardiac Pacing, Artificial; D004553:Electric Conductivity; D006325:Heart Atria / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism; D011817:Rabbits; D013997:Time Factors
D015220:Calcium Channels; D015221:Potassium Channels; D011188:Potassium