Which of the following is/are true about ADH?
a. It promotes obligatory water reabsorption
b. It is secreted in response to an increase in extracellular fluid osmolality
c. It causes insertion of aquaporins in the PCT
d. It promotes Na⁺ reabsorption

Verified step by step guidance

Step 1: Understand the role of ADH (antidiuretic hormone), also known as vasopressin, which primarily regulates water balance in the body by controlling water reabsorption in the kidneys.

Step 2: Analyze option (a): ADH promotes water reabsorption, but specifically in the collecting ducts, not the proximal convoluted tubule (PCT). It mainly affects facultative water reabsorption rather than obligatory water reabsorption, which occurs in the PCT regardless of ADH.

Step 3: Analyze option (b): ADH secretion is stimulated by an increase in extracellular fluid osmolality, meaning when the body detects higher solute concentration, ADH is released to conserve water and dilute the plasma.

Step 4: Analyze option (c): ADH causes insertion of aquaporin-2 water channels in the collecting ducts, not in the PCT. Aquaporins in the PCT are constitutively present and not regulated by ADH.

Step 5: Analyze option (d): ADH does not directly promote sodium (Na⁺) reabsorption; its main effect is on water permeability. Sodium reabsorption is primarily regulated by aldosterone and other mechanisms.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Antidiuretic Hormone (ADH) Function

ADH, also known as vasopressin, primarily regulates water balance by increasing water reabsorption in the kidneys. It acts mainly on the collecting ducts, making them more permeable to water, which helps concentrate urine and reduce water loss.

Regulation of ADH Secretion

ADH secretion is triggered by increased plasma osmolality, detected by osmoreceptors in the hypothalamus. When extracellular fluid becomes more concentrated, ADH release increases to conserve water and restore osmotic balance.

Aquaporin Insertion and Site of Action

ADH promotes the insertion of aquaporin-2 water channels into the apical membrane of collecting duct cells, enhancing water reabsorption. This effect does not occur in the proximal convoluted tubule (PCT), where water reabsorption is mostly obligatory and not regulated by ADH.

Recommended video:

Guided course