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The epithelial sodium channel (ENaC), (also known as amiloride-sensitive sodium channel) is a membrane-bound ion channel that is selectively permeable to sodium ions (Na +).It is assembled as a heterotrimer composed of three homologous subunits α or δ, β, and γ, [2] These subunits are encoded by four genes: SCNN1A, SCNN1B, SCNN1G, and SCNN1D.
Aldosterone stimulates Na + and water reabsorption from the gut, salivary and sweat glands in exchange for K +. Aldosterone stimulates secretion of H + via the H+/ATPase in the intercalated cells of the cortical collecting tubules; Aldosterone upregulates expression of NCC in the distal convoluted tubule chronically and its activity acutely. [18]
The inactivating mutation leads to elevated local concentrations of cortisol in the aldosterone sensitive tissues like the kidney. Cortisol at high concentrations can cross-react and activate the mineralocorticoid receptor due to the non-selectivity of the receptor, leading to aldosterone-like effects in the kidney.
The mineralocorticoid receptor (or MR, MLR, MCR), also known as the aldosterone receptor or nuclear receptor subfamily 3, group C, member 2, (NR3C2) is a protein that in humans is encoded by the NR3C2 gene that is located on chromosome 4q31.1-31.2. [5] MR is a receptor with equal affinity for mineralocorticoids and glucocorticoids.
ENaC is assembled as a heterotrimer composed of three homologous subunits α, β, and γ or δ, β, and γ. The other ENAC subunits are encoded by SCNN1A, SCNN1G, and SCNN1D. [5] ENaC is expressed in epithelial cells [5] and is different from the voltage-gated sodium channel that is involved in the generation of action potentials in neurons ...
In Liddle's syndrome, ENaC-binding potassium-sparing diuretics (e.g. amiloride or triamterene) are used to counter the excess ENaC activity. [4] [10] [2] In AME, the mineralocorticoid receptor-binding potassium-sparing diuretics (e.g. spironolactone or eplerenone) are used to limit aldosterone receptor activity. [1]
It selectively stimulates secretion of aldosterone. The secretion of aldosterone has a diurnal rhythm. Control of aldosterone release from the adrenal cortex: [citation needed] The role of the renin–angiotensin system: Angiotensin is involved in regulating aldosterone and is the core regulator. Angiotensin II acts synergistically with potassium.
SCNN1A, SCNN1B, and SCNN1G are commonly expressed in tight epithelia that have low water permeability. The major organs where ENaC is expressed include parts of the kidney tubular epithelia, [5] [7] [17] the respiratory airway, [18] the female reproductive tract, [18] male reproductive tract, including testis, spermatogonia in the seminiferous tubules, Sertoli cells, and spermatozoa, [19 ...