Question:
Theophylline causes diuresis by which of the following mechanisms?
Theophylline causes diuresis by which of the following mechanisms?
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Methylxanthines block a purine receptor in the proximal tubule to cut sodium reabsorption.
Updated On: Jun 23, 2026
- PDE3 inhibition
- PDE4 inhibition
- Beta-2 agonist action
- Adenosine A1 receptor antagonism
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The Correct Option is D
Solution and Explanation
Step 1: Theophylline is a methylxanthine. Its mild diuretic action comes from inhibiting tubular fluid reabsorption in the renal proximal tubule, not from increasing cardiac output alone.
Step 2: Studies with selective adenosine antagonists and A1 receptor knockout mice show diuresis is lost when the A1 adenosine receptor (A1AR) is deleted. So theophylline produces diuresis mainly by blocking adenosine A1 receptors in the proximal tubule, reducing Na+ and water reabsorption.
Step 3: It is also a weak renal vasodilator and antagonises adenosine-induced preglomerular vasoconstriction, and it stimulates renin secretion by blocking adenosine receptors. While PDE inhibition explains its bronchodilator and cardiac actions, the diuresis is driven by adenosine A1 antagonism.
Ref: NCBI / renal pharmacology of methylxanthines.
Step 2: Studies with selective adenosine antagonists and A1 receptor knockout mice show diuresis is lost when the A1 adenosine receptor (A1AR) is deleted. So theophylline produces diuresis mainly by blocking adenosine A1 receptors in the proximal tubule, reducing Na+ and water reabsorption.
Step 3: It is also a weak renal vasodilator and antagonises adenosine-induced preglomerular vasoconstriction, and it stimulates renin secretion by blocking adenosine receptors. While PDE inhibition explains its bronchodilator and cardiac actions, the diuresis is driven by adenosine A1 antagonism.
Ref: NCBI / renal pharmacology of methylxanthines.
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