Question

Which of the following causes an increase in sodium reabsorption in the distal convoluted tubule?

• A. Increase in aldosterone levels.
• B. Increase in antidiuretic hormone levels.
• C. Decrease in aldosterone levels.
• D. Decrease in antidiuretic hormone levels.

Answer 1

Answer: (A)

Aldosterone is a hormone secreted by the outer layer of the adrenal gland (cortex part). Decreased blood volume and interstitial fluid level, resulting in decreased blood pressure, trigger aldosterone secretion. When aldosterone is present in the blood, reabsorption of Na⁺in the filtrate is increased by the epithelial cells of the collecting duct. Retaining Na⁺, raises the osmotic pressure of the blood and reduces water loss from the body. When "aldosterone is absent, some Na⁺remains in the filtrate and" is excreted with the urine.