Immunology USMLE Step 1 Practice Question
A 6-year-old boy presents with nonbloody watery diarrhea after visiting relatives in a rural area. Vital signs show HR 110/min, BP 95/60 mmHg, temperature 37.2°C, and mild dehydration. Stool culture grows enterotoxigenic Escherichia coli producing heat-stable toxin. Serum electrolytes show hypokalemia (K+ 3.1 mEq/L). No bloody stools or fever. Which second messenger is most directly increased by this toxin's mechanism of action?
Answer choices
- ACyclic GMPCorrect answer
- BCalmodulin
- CCyclic AMP
- DInositol triphosphate
- EDiacylglycerol
- FCalcium/calmodulin-dependent protein kinase II
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