"Creep currents" in single frog atrial cells may be generated by electrogenic Na/Ca exchange

Area of Science:

• Cardiology
• Cell Physiology
• Biophysics

Background:

• Na loading in single frog atrial cells induces "creep currents."
• The underlying mechanism of these currents remains to be fully elucidated.

Purpose of the Study:

• To test the hypothesis that electrogenic Na/Ca exchange generates creep currents.
• To characterize the properties of creep currents across a range of membrane potentials.

Main Methods:

• Voltage-clamp technique applied to single frog atrial cells.
• Examination of creep currents during depolarizing and hyperpolarizing voltage pulses.
• Optical monitoring of cellular mechanical activity.

Main Results:

• Inward and outward creep currents exhibited a common reversal potential, suggesting a shared generation mechanism.
• Creep current properties were voltage-dependent and sensitive to preceding pulse conditions.
• A strong correlation was observed between creep currents and cellular mechanical activity (contraction/relaxation).

Conclusions:

• The findings support the hypothesis that electrogenic Na/Ca exchange is responsible for creep currents in frog atrial cells.
• A mathematical model of Na/Ca exchange adequately explains observed creep current characteristics.