2-APB induces instability in rat left atrial mechanical activity

Area of Science:

• Cardiology
• Physiology
• Pharmacology

Background:

• Atrial contractile abnormalities are prevalent clinical issues.
• Existing pharmacological models for studying these abnormalities in isolated atrial muscle are limited.
• Sarcoplasmic reticulum (SR) calcium leak is a potential underlying mechanism for atrial contractile irregularities.

Purpose of the Study:

• To investigate the effects of 2-aminoethoxydiphenyl borate (2-APB), a known calcium leak-inducer, on the mechanical function of isolated rat left atria.
• To determine if 2-APB can reliably induce abnormalities in atrial contractility.
• To explore the ionic mechanisms underlying 2-APB-induced atrial mechanical dysfunction.

Main Methods:

• Isolated, superfused rat left atria were used.
• Atria were paced at 3 Hz and exposed to varying concentrations of 2-APB.
• Ionic gradients (sodium, chloride) and membrane potential were manipulated to assess their effects on 2-APB-induced activity.

Main Results:

• Exposure to >10 microM 2-APB induced sporadic mechanical events independent of the pacing stimulus.
• Prolonged diastole in the presence of 2-APB led to spontaneous mechanical activity (SMA).
• SMA was dependent on atrial sodium and chloride gradients and sensitive to membrane potential changes, suggesting involvement of ion channels and transporters.

Conclusions:

• 2-aminoethoxydiphenyl borate (2-APB) effectively induces instability in regular atrial mechanical activity, establishing a novel pharmacological model for atrial contractile abnormalities.
• The observed spontaneous mechanical activity is linked to sodium and chloride gradients and potentially membrane potential.
• The findings suggest that 2-APB-induced atrial dysfunction may involve forward-mode sodium-calcium exchange and chloride channel activities, and may decrease SR calcium levels.