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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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Nitric oxide is synthesised from:
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The correct answer is  NO is synthesized from l-arginine by the enzyme nitric oxide synthase (NOS). There are three different types of NOS: endothelial (eNOS), neuronal (nNOS), and inducible (iNOS). eNOS and nNOS are constitutively expressed at low levels and can be activated rapidly by an increase in cytoplasmic Ca2+. iNOS, in contrast, is induced when macrophages and other cells are activated by cytokines (e.g., TNF, IFN-g) or microbial products. Ref: Robbins 8th edition, Chapter 2.