The changes of potassium currents in rabbit ventricle with healed myocardial infarction

Abstract

To elucidate the mechanism of arrhythmia in healed myocardial infarction (HMI), the changes of action potential duration (APD), transient outward potassium current (1_ω), delayed rectifier potassium current (I_k) and inward rectifier potassium current (I_ki) of left ventricular myocytes in non-infarcted zone of HMI were investigated. Rabbits were randomly assigned into two groups: HMI group, in which animals were subjected to thoracotomy and ligation of the circumflex coronary and sham-operated group, in which rabbits underwent thoracotomy but no conorary ligation. 3 months after the operation, the whole myocyte patch clamp technique was used to record APD, I_to I_k, and I_ki of ventricular myocytes in non-infarcted zone. Our results showed that the membrane capacitance was larger in HMI group than in sham-operated group. Action potential duration was significantly lengthened in HMI group and early afterdepolarization (EAD) appeared in HMI group. The densities of I_to, K_{k, tail}, and K_ki were reduced significantly in HMI group, from 6. 72±0.42 pA/pF, 1.54±0.13 pA/pF and 25.6±2.6 pA/pF in sham-operated group to 4.03±0.33 pA/pF, 1.14±0.11 pA/pF and 17.6±2.3 pA/pF, respectively. It is concluded that the reduced densities of I_to, I_k.tail and I_ki in ventricular myocytes of non-infarcted zone in HMI were responsible for the prolongation of APD and the presentation of EAD which played important roles in the development of malignant arrhythmia in HMI.

Keywords

myocardial infarction / potassium currents / patch clamp

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