K+-free induced early afterdepolarization in cardiac ventricular fibers of guinea pig after cold treatment.
The genesis and elimination of early afterdepolarizations (EADs) have been investigated in guinea pig cardiac ventricular fibers after a short period of cooling (5 h, 2-4 degrees C). After rewarming them to 37 degrees C, EADs could be induced by K+-free superfusion at an appropriate driving stimulation (0.2 Hz) in all preparations. A high level plateau, which linearly increases its duration with time, appears ahead of EADs. The critical point of the plateau occurred steadily, at the level of -47 +/- 4 mV. Two types of triggered activity, all of which are the rhythmic activities in low level of membrane potential (-50 to -60 mV), appear on the plateau. There is no significant change after overdriving. Agonists of the Na-K pump (K+ and T1+) could stop the rhythmic activity immediately and turn the low level of membrane potential to high one. The results showed that high level plateau is the basis of genesis of EADs, and the activation of Na-K pump plays an important part in stopping triggered rhythms arising from EADs.
Wang
Z M
ZM
Department of Biology, Peking University.
Liu
T F
TF
Liu
K Q
KQ
D000818:Animals; D006168:Guinea Pigs; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles; D007036:Hypothermia, Induced; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D011188:Potassium / Q000494:pharmacology; D015222:Sodium Channels; D013793:Thallium / Q000494:pharmacology
D015222:Sodium Channels; D013793:Thallium; D011188:Potassium