Epithelial sodium channel

The epithelial sodium channel (ENaC), (also known as amiloride-sensitive sodium channel) is a membrane-bound <a href="/facts/Ion_channel/A46LARFH">ion channel</a> that is selectively permeable to <a href="/facts/Sodium/eYuSPu2V">sodium</a> <a href="/facts/Ion/3bePpDna">ions</a> (Na+). It is assembled as a heterotrimer composed of three homologous subunits α or δ, β, and γ, These subunits are encoded by four genes: <a href="/facts/SCNN1A/H4eB0slD">SCNN1A</a>, <a href="/facts/SCNN1B/EMz2tXuk">SCNN1B</a>, <a href="/facts/SCNN1G/LKq5U5sB">SCNN1G</a>, and <a href="/facts/SCNN1D/xo47DmWC">SCNN1D</a>. The ENaC is involved primarily in the reabsorption of sodium ions at the <a href="/facts/Collecting_duct/MmpNcpLA">collecting ducts</a> of the <a href="/facts/Kidney/HBspPrv9">kidney</a>'s <a href="/facts/Nephron/ss24U1zW">nephrons</a>. In addition to being implicated in diseases where fluid balance across epithelial membranes is perturbed, including pulmonary edema, cystic fibrosis, COPD and COVID-19, proteolyzed forms of ENaC function as the human salt taste receptor.
The apical membranes of many tight epithelia contain <a href="/facts/Sodium_channel/pXb4n2Vz">sodium channels</a> that are characterized primarily by their high affinity for the <a href="/facts/Diuretic/x3j4I1Tg">diuretic</a> blocker <a href="/facts/Amiloride/JlcLDbvd">amiloride</a>. These channels mediate the first step of active sodium reabsorption essential for the maintenance of body salt and water homeostasis. In <a href="/facts/Vertebrate/tT54FSTT">vertebrates</a>, the channels control reabsorption of sodium in kidney, colon, lung and sweat glands; they also play a role in taste perception.
The epithelial sodium channels are structurally and probably evolutionary related to <a href="/facts/P2X_purinoreceptor/oCYaQG5I">P2X purinoreceptors</a>, pain receptors that activate when they detect ATP.

Epithelial sodium channel open-in-new

Epithelial sodium channel