Oral rehydration therapy remains effective even in cholera, where cAMP driven chloride secretion is maximal. The physiological basis for this efficacy is:
- A The apical SGLT1 sodium-glucose cotransporter is unaffected by cAMP, so coupled Na and glucose absorption continues and drags water across ✓
- B Glucose downregulates the cystic fibrosis transmembrane regulator and closes chloride secretion
- C Oral sodium bypasses the enterocyte through solvent drag across tight junctions
- D Glucose stimulates enteric secretomotor neurons to switch the crypt to absorptive mode
Correct answer: A. The apical SGLT1 sodium-glucose cotransporter is unaffected by cAMP, so coupled Na and glucose absorption continues and drags water across
Explanation
Glucose coupled sodium absorption through the apical SGLT1 cotransporter is independent of cAMP and remains fully functional in cholera. Adding glucose to oral fluids allows sodium uptake, and water follows osmotically through the transcellular route, offsetting the secretory losses. This is why WHO oral rehydration solutions contain both sodium and glucose. Chloride channels are not closed by glucose, and the effect is transcellular rather than paracellular.
Reference: Ganong Review of Medical Physiology, 27th ed.
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