Sodium Channels

Sodium channels are integral membrane proteins that form a Na⁺ permeable pore through the plasma membrane and allow ion flux. There are two very different types of sodium channels: voltage-gated sodium channels (Na_V) and epithelial sodium channels (ENaC). Na_V are present in the membrane of most excitable cells and exist as heterodimers or heterotrimers of 1 α- and 1 or 2 β-subunits. ENaC are present in absorptive epithelia, such as the distal kidney tubule, alveolar epithelium and distal colon, and are responsible for sodium reabsorption. They exist as heterotetramers of α-, β- and γ-subunits, the predominant one being 2α:1β:1γ.