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Isolation of Human Atrial Myocytes for Simultaneous Measurements of Ca2+ Transients and Membrane Currents
10:53

Isolation of Human Atrial Myocytes for Simultaneous Measurements of Ca2+ Transients and Membrane Currents

Published on: July 3, 2013

Amiloride and KB-R7943 in outward Na+ /Ca2+ exchange current in guinea pig ventricular myocytes

Jing Lu1, Yong Liang, Xiaoliang Wang

  • 1Department of Pharmacology, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.

Journal of Cardiovascular Pharmacology
|June 20, 2002
PubMed

Insights

Amiloride and KB-R7943 were tested for their effects on sodium-calcium exchanger (NCX) activity in heart cells. KB-R7943 inhibited both forward and reverse NCX modes equally, suggesting it is not a selective inhibitor for the reverse mode.

Area of Science:

  • Cardiology
  • Molecular Physiology
  • Pharmacology

Background:

  • The reverse mode of the sodium-calcium exchanger (NCX) plays a critical role in calcium overload during cardiac ischemia and reperfusion.
  • Understanding the modulators of NCX activity is crucial for developing therapeutic strategies against heart damage.

Purpose of the Study:

  • To investigate the inhibitory effects of amiloride and KB-R7943 on the Na+/Ca2+ exchange current (INa/Ca) in guinea pig ventricular myocytes.
  • To determine the selectivity of KB-R7943 on the reverse mode of NCX.

Main Methods:

  • Whole-cell patch clamp techniques were employed to measure INa/Ca.
  • Experiments were conducted under bidirectional ionic conditions with a specific pipette solution (25 mM Na+).
  • The effects of varying concentrations of amiloride and KB-R7943 on both outward and inward INa/Ca were assessed at different membrane potentials (+50 mV and -80 mV).

Main Results:

  • Amiloride demonstrated a dose-dependent inhibition of both outward and inward INa/Ca, with a greater effect on the outward current.
  • KB-R7943 also inhibited outward and inward INa/Ca in a dose-dependent manner.
  • KB-R7943 exhibited similar potency in inhibiting both directions of the Na+/Ca2+ exchange current.

Conclusions:

  • Amiloride inhibits both modes of Na+/Ca2+ exchange, but with greater efficacy on the outward current.
  • KB-R7943 is not a selective inhibitor of the reverse mode of Na+/Ca2+ exchange, as it affects both forward and reverse modes equally.
  • These findings have implications for the use of these agents in conditions involving altered NCX activity, such as ischemia-reperfusion injury.

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