Question

why is Aldosterone is the primary control of sereum Na+ levels?

Answer 1

Aldosterone is the primary control for maintaining serum Sodium levels because:

• Aldosterone helps in reabsorption of sodium in (ascending limb, distal convoluted tubule, collecting duct of) renal tubules which accounts for major portion of sodium reabsorption
• Sodium reabsorption is accompanied by water reabsorption which helps in maintenance of the osmolarity of the body fluids.
• The transport of sodium ions from lumen of renal tubules to the tubular epithelial cells by Sodium antiport and Sodium co-transport mechanisms which are mediated by Sodium counterport protein and sodium co transport protein respectively both of which are positively influenced by Aldosterone
• The transport of sodium ions from tubular cells to interstitial fluid by sodium potassium pump is also controlled by Aldosterone
• Finally the entry of sodium ions into the peritubular capillaries is also facilitated by Aldosterone.

Hence, Aldosterone is responsible for 99% reabsorption of sodium present in glomerular filtrate which is accompanied by water reabsorption. This increases the serum level of sodium and hence, aldosterone is considered as primary control of serum sodium levels.