What are the major functions of "P" cells present in coical collecting ducts?

Sodium & water reabsorption from the lumen.Potassium secretion into the lumen.ADH controlled water reabsorption.FUNCTIONS OF 'P' CELLS:1. Sodium & water reabsorption:Reabsorbed from lumen.Occurs through Na2+ channels (ENaC channels). Approximately 3% Na reabsorption occurs.2. Potassium secretion:Secreted into lumen.K+ both secreted & reabsorbed.Note: Na2+ reabsorption & K+ secretion depends on,Na2+-K+-ATPase activity in basolateral membrane.Aldosterone.3. Water reabsorption:ADH Controlled.Stimulates water channel, aquaporin-2.