Question

Which of the following hormone stimulates Na + (sodium ion) retention?

• A. Adrenaline
• B. Aldosterone
• C. Cortisol
• D. Oestrogen

Hint:

Renal Electrolyte Control:
Aldosterone $\rightarrow \text{Na}^+$ Retention & $\text{K}^+$ Excretion.
ANP (Atrial Natriuretic Peptide) $\rightarrow \text{Na}^+$ Excretion (Natriuresis).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Mineralocorticoids regulate renal electrolyte and extracellular fluid volume homeostasis via genomic upregulation of epithelial sodium channels (ENaC) and $ ext{Na}^+/ ext{K}^+$-ATPase pumps.
Key Formula or Approach:
\[ \text{Aldosterone} \xrightarrow{\text{Distal Tubule / Collecting Duct}} \uparrow \text{ENaC} + \uparrow \text{Na}^+/\text{K}^+\text{-ATPase} \implies \text{Na}^+\text{ Retention} + \text{K}^+/\text{H}^+\text{ Excretion} \]

Step 2: Detailed Explanation:
Aldosterone (the primary mineralocorticoid synthesized by the adrenal cortex zona glomerulosa):
- Binds to intracellular mineralocorticoid receptors in the principal cells of the renal distal convoluted tubules and cortical collecting ducts.
- Upregulates apical Epithelial Sodium Channels (ENaC) and basolateral $\text{Na}^+/\text{K}^+$-ATPase pumps, maximally promoting sodium ion ($\text{Na}^+$) reabsorption/retention into peritubular capillaries while stimulating potassium ($\text{K}^+$) and proton ($\text{H}^+$) secretion into tubular urine.

Step 3: Final Answer:
Thus, Aldosterone stimulates Na+ retention, matching option (B).