Intracellular magnesium affects I(K) in single frog atrial cells

Area of Science:

• Cardiovascular Physiology
• Electrophysiology
• Cellular Biology

Background:

• Potassium currents (IK) are critical for cardiac action potential regulation.
• Intracellular ion concentrations, particularly magnesium, can modulate ion channel function.

Purpose of the Study:

• To investigate the effect of intracellular magnesium concentration on voltage- and time-dependent potassium current (IK) in frog atrial cells.
• To determine if magnesium's influence on IK is specific or related to solution properties like ionic strength.

Main Methods:

• Whole-cell voltage-clamp recordings were performed on single frog (Rana pipiens) atrial cells.
• Patch pipette solutions with varying magnesium chloride (MgCl2) concentrations (0-10 mM) were used.
• Control solutions with other chloride salts were employed to assess non-specific effects.

Main Results:

• Increasing intracellular MgCl2 concentration suppressed the magnitude of IK.
• 10 mM MgCl2 enhanced the activation rate of IK, while lower concentrations had no significant effect.
• Effects were specific to magnesium and not due to changes in ionic strength, osmolality, or chloride concentration.

Conclusions:

• Intracellular magnesium concentration directly influences the voltage- and time-dependent potassium current (IK) in frog atrial cells.
• Magnesium plays a regulatory role in cardiac electrophysiology by modulating potassium channel activity.
• These findings highlight the importance of intracellular magnesium homeostasis for normal heart function.