Which of the following is false regarding nitric oxide?: (A) Derived from endothelium, (B) Acts by increasing cAMP levels, (C) Vasodilator, (D) Derived from arginine
Answer is B. 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