Water Channel

A water channel is a specialized membrane protein that facilitates the rapid and selective movement of water molecules across biological membranes.

• ✅ Selectivity: Permits only water molecules (and sometimes small solutes like glycerol).
• 🚰 Passive transport: Water moves via osmosis, requiring no energy (ATP).
• ⏱️ High throughput: Each channel can transport billions of water molecules per second.

Water channels are crucial in maintaining fluid balance in various tissues and organs:

• Kidneys – Concentration of urine.
• Brain – Water regulation in astrocytes (especially via AQP4).
• Glands – Saliva and tear production.
• Skin – Hydration and barrier function.

The best-known water channels are aquaporins. Examples include:

• AQP1 – Present in red blood cells and kidney tubules.
• AQP2 – Regulated by vasopressin in kidney collecting ducts.
• AQP4 – Abundant in the brain and spinal cord, involved in neuroinflammation and edema.

• Wikipedia: Aquaporin
• Review Article on Aquaporins – NCBI