This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
Which of the following is false regarding nitric oxide? 
Select and explain. 
A. Derived from endothelium, B. Acts by increasing cAMP levels, C. Vasodilator, D. Derived from arginine
B: Acts by increasing cAMP levels
Answer: B: Acts by increasing cAMP levels 
Explanation: Nitric oxide acts by increasing cGMP not by increasing cAMP. Nitric Oxide: Also known as Endothelium-derived relaxing factor (EDRF) Synthesized in endothelial cells from arginine in a reaction catalyzed by nitric oxide synthase(NOS) Mechanism of Action: NO causes activation of guanylyl cyclase - Increased cGMP - relaxation of smooth muscle - vasodilation. Effects of NO: Vasodilation Neuromodulator in brain Antimicrobial and cytotoxic activity of various inflammatory cells. In GIT, relaxation of smooth muscle. Penile erection. Ref: Ganong&;s Review of Medical Physiology 26th edition Pgno: 583-584