Tolvaptan is a selective V2 receptor antagonist approved for autosomal dominant polycystic kidney disease (ADPKD). The mechanism by which V2 blockade slows renal cyst growth is:
- A V2 receptor blockade reduces cAMP in collecting duct epithelial cells; in PKD1/PKD2 mutations, elevated cAMP is a primary driver of mTOR-independent cyst epithelial proliferation and fluid secretion via CFTR — blocking V2 reduces the cAMP signal driving cyst expansion ✓
- B V2 receptor blockade reduces aquaporin-2 insertion in the collecting duct, decreasing water reabsorption and concentrating polycystic kidney tubular fluid
- C V2 receptor blockade reduces renal prostaglandin E2, which otherwise stimulates polycystin-1-deficient tubular epithelial cells to proliferate
- D Vasopressin V2 stimulation upregulates TGF-β in collecting duct; tolvaptan blocks this fibrogenic pathway to slow renal scarring around cysts
Explanation
In ADPKD (PKD1 or PKD2 mutations causing polycystin-1/-2 dysfunction), the cellular pathomechanism includes dysregulated cAMP signaling: elevated cAMP drives cyst epithelial cell proliferation (through B-Raf/MEK/ERK pathway) and CFTR-mediated chloride and fluid secretion into cyst lumens, expanding cyst volume. Vasopressin acts on V2 receptors in collecting duct cells, generating cAMP via adenylyl cyclase activation; in ADPKD tubular cells, this cAMP is exaggerated due to polycystin dysfunction. Tolvaptan (TEMPO 3:4 and REPRISE trials) suppresses this cAMP-driven cyst growth. Aquaporin-2 effects (water reabsorption) are a secondary consequence but not the ADPKD-relevant mechanism. The hepatotoxicity risk of tolvaptan (FDA black box warning) limits its use to patients at high risk of rapid progression.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.