Cholera toxin produces profuse rice-water diarrhoea by which specific mechanism?
- A Directly destroying intestinal epithelial cells and causing haemorrhagic ulcers
- B Irreversible activation of adenylate cyclase via ADP-ribosylation of Gs-α subunit, causing massive Cl⁻ secretion ✓
- C Blocking Na⁺/K⁺-ATPase on enterocytes, impairing sodium absorption
- D Activating PLC-mediated IP3 pathway causing intracellular Ca²⁺ release
Explanation
Cholera toxin (CT) is an AB5 toxin: the B subunit binds GM1 ganglioside on enterocyte membranes; the A subunit ADP-ribosylates the Gs-α subunit of adenylate cyclase, locking it in the active state. This leads to sustained elevation of cAMP, which activates PKA, phosphorylates CFTR, and causes massive Cl⁻ (and Na⁺ and H₂O) secretion into the gut lumen — producing profuse, isotonic, watery 'rice-water' diarrhoea of up to 20 L/day. Mucosal architecture is preserved (no haemorrhage). Treatment is oral rehydration solution exploiting intact glucose-Na⁺ co-transport.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.