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Related Experiment Videos

Membrane resistance increases when automaticity develops in explanted rat heart cells.

O F Schanne1, M Lefloch, B Fermini

  • 1Département de Biophysique, Faculté de Médecine, Université de Sherbrooke, Quebec, Canada.

The American Journal of Physiology
|January 1, 1990
PubMed
Summary

Neonatal rat ventricle cells develop spontaneous activity due to decreased inwardly rectifying potassium (K+) conductance (gk1), not just voltage-dependent membrane resistance. Some inward-rectifying channels become silent during this process.

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Area of Science:

  • Cardiovascular Physiology
  • Electrophysiology
  • Cell Biology

Background:

  • Neonatal rat ventricular cells exhibit spontaneous electrical activity, unlike adult myocytes.
  • Understanding the electrical property changes is crucial for studying cardiac development and arrhythmias.

Purpose of the Study:

  • To compare the passive electrical properties of isolated adult ventricular myocytes with cultured neonatal rat ventricle cells.
  • To elucidate the mechanisms underlying the development of spontaneous activity in neonatal rat ventricular cells.

Main Methods:

  • Patch-clamp electrophysiology to measure membrane potential, action potentials, and current-voltage relationships.
  • Comparison of electrical properties between isolated adult myocytes and cultured neonatal cells.
  • Modeling using a finite disk to determine membrane parameters.

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Main Results:

  • Neonatal cells showed a less negative resting potential (-50 mV vs. -65 mV) and spontaneous activity, unlike adult myocytes.
  • Specific membrane resistance in adult myocytes was voltage-dependent, increasing with depolarization.
  • In cultured neonatal cells, input resistance decreased with increasing external K+ concentration, indicating anomalous rectification. A decrease in inwardly rectifying potassium conductance (gk1) was identified as the primary cause for increased membrane resistance and depolarization.
  • Approximately 41% of inward-rectifying channels were found to be electrically silent in spontaneously active neonatal cells.

Conclusions:

  • The voltage dependence of membrane resistance alone does not fully explain the increased resistance observed with spontaneous activity.
  • A reduction in inwardly rectifying potassium conductance (gk1) is the main driver of increased membrane resistance and depolarization in developing neonatal rat ventricular cells.
  • A significant portion of inward-rectifying channels become electrically silent as spontaneous activity emerges in these cells.