What is the role of aldosterone in regulating fluid balance?

• A. Inhibits sodium reabsorption
• B. Promotes sodium reabsorption and potassium excretion
• C. Enhances water loss through urine
• D. Regulates body temperature

Answer: (B)

Aldosterone plays a crucial role in regulating fluid balance within the body by promoting sodium reabsorption in the kidneys. This hormone, produced by the adrenal cortex, acts on the distal convoluted tubules and collecting ducts of the nephron, enhancing the reabsorption of sodium ions from the renal tubular fluid into the bloodstream. This reabsorption not only increases sodium levels in the blood but also leads to water retention, as water follows sodium osmotically.

In addition to sodium reabsorption, aldosterone also promotes the excretion of potassium in the urine, which helps to maintain proper electrolyte balance. The increase in sodium reabsorption ultimately contributes to an increase in blood volume and blood pressure, helping to ensure that the body's fluid balance remains stable.

Other options, while discussing aspects of fluid and electrolyte balance, do not accurately reflect the primary function of aldosterone. The role of inhibiting sodium reabsorption, enhancing water loss, or regulating body temperature does not align with the established physiological function of aldosterone in fluid and electrolyte homeostasis.