Question

Aldosterone regulates the water and electrolyte balance in the human body by

• A. Stimulating the H₂O and Na⁺ reabsorption, while K⁺ and PO₄³⁻ excretion
• B. Stimulating the Na⁺ and K⁺ reabsorption, while H₂O and PO₄³⁻ excretion
• C. Stimulating the H₂O reabsorption and Na⁺ excretion
• D. Stimulating the Na⁺ and PO₄^3- reabsorption, while K⁺ excretion

Hint:

Remember: Aldosterone saves Nasuperscript{+} and water, and kicks out Ksuperscript{+}. It helps in increasing blood volume and pressure by reabsorbing sodium and water.

Answer 1

The Correct Option is A

Step 1: Understand the role of aldosterone.
Aldosterone is a mineralocorticoid hormone secreted by the adrenal cortex. It plays a critical role in maintaining sodium and potassium levels in the body, thereby helping to regulate blood pressure and fluid balance. 
Step 2: Mechanism of action.
Aldosterone acts mainly on the distal convoluted tubules and collecting ducts of the nephrons in the kidneys. Its effects include:
Increasing reabsorption of sodium ions (Na⁺) into the blood.
Promoting reabsorption of water (H₂O) indirectly, because water follows sodium osmotically.
Enhancing excretion of potassium ions (K⁺) into the urine.
Promoting excretion of phosphate ions (PO₄^3-) as a part of maintaining electrolyte balance.
Step 3: Evaluate the options.
Option (1): Correct — This matches the physiological role of aldosterone.
Option (2): Incorrect — Aldosterone does not stimulate K⁺ reabsorption.
Option (3): Incorrect — Aldosterone promotes Na⁺ reabsorption, not its excretion.
Option (4): Incorrect — Aldosterone promotes K⁺ excretion, but not PO₄^3- reabsorption.