During reperfusion injury following myocardial ischaemia, massive superoxide generation occurs from multiple sources. The enzyme responsible for the BURST of superoxide from neutrophils recruited to infarcted myocardium is:
- A NADPH oxidase (NOX2) ✓
- B Xanthine oxidase
- C Mitochondrial complex I
- D Myeloperoxidase
Explanation
Neutrophils recruited to ischaemia-reperfusion injury undergo respiratory burst mediated by NADPH oxidase (NOX2/gp91phox), generating massive superoxide (O2•-) by transferring electrons from NADPH to molecular oxygen. Assembly of the active phagocyte NADPH oxidase complex (gp91phox, p22phox, p47phox, p67phox, p40phox, and Rac2) at the membrane is triggered by neutrophil activation. Xanthine oxidase (from endothelial cell xanthine dehydrogenase converted during ischaemia) is a significant source in the endothelium during early reperfusion, not neutrophils. Mitochondrial complex I generates superoxide during electron transport uncoupling. Myeloperoxidase uses H2O2 to generate HOCl but is not directly responsible for superoxide burst.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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