Potassium ion gradient across cardiomyocyte membrane (K+ gradient)

The potassium ion gradient across the cardiomyocyte membrane is the concentration difference between intracellular potassium (approximately 140-150 mM) and extracellular potassium (approximately 4 mM), maintained primarily by the Na+/K+-ATPase pump (StatPearls, 2023). This electrochemical gradient is the fundamental determinant of the resting membrane potential and provides the driving force for the repolarization phase of the cardiac action potential (PubMed, PMID: 11340003). It is regulated by a diverse array of potassium-selective ion channels, such as the inward rectifier (Kir) and voltage-gated (Kv) channels, which allow K+ to flow out of the cell down its chemical gradient (UniProt, P12235). Clinical disturbances in this gradient, such as hyperkalemia or hypokalemia, significantly alter cardiac excitability and can lead to lethal arrhythmias like ventricular fibrillation (NIH, 2022). Many cardiovascular drugs, including Class III antiarrhythmics like Amiodarone and cardiac glycosides like Digoxin, exert their effects by modulating the proteins that establish or utilize this gradient (PubChem, CID 2157). Consequently, maintaining this gradient is critical for normal heart rhythm, and it serves as a central focus for antiarrhythmic drug therapy and electrolyte management in clinical practice (StatPearls, 2023).

Other names

Transmembrane potassium gradientCardiac potassium gradientIntracellular-extracellular potassium ratioK+ concentration gradient

Drugs modulate the gradient by inhibiting or activating ion transporters (e.g., Na+/K+-ATPase) or ion channels (e.g., voltage-gated potassium channels) that regulate the flux of K+ ions across the sarcolemma (StatPearls, 2023).