Which gas is associated with the mechanism of action of drugs like nitroglycerin and sildenafil?

Which gas is associated with the mechanism of action of drugs like nitroglycerin and sildenafil?

• A. NO
• B. N2O
• C. CO2
• D. NO2

Answer: (A)

Nitric oxide is the signaling gas involved. Nitric oxide released from nitroglycerin activates soluble guanylate cyclase in vascular smooth muscle, increasing cGMP levels. That cGMP lowers intracellular calcium and causes relaxation, leading to vasodilation. Sildenafil then helps by inhibiting phosphodiesterase-5, the enzyme that degrades cGMP, so the NO-cGMP signal lasts longer and enhances vasodilation. The other gases don’t participate in this pathway: nitrous oxide is a separate anesthetic gas, carbon dioxide isn’t the signaling molecule driving this relaxation, and nitrogen dioxide is not involved in this mechanism.

Nitric oxide is the signaling gas involved. Nitric oxide released from nitroglycerin activates soluble guanylate cyclase in vascular smooth muscle, increasing cGMP levels. That cGMP lowers intracellular calcium and causes relaxation, leading to vasodilation. Sildenafil then helps by inhibiting phosphodiesterase-5, the enzyme that degrades cGMP, so the NO-cGMP signal lasts longer and enhances vasodilation. The other gases don’t participate in this pathway: nitrous oxide is a separate anesthetic gas, carbon dioxide isn’t the signaling molecule driving this relaxation, and nitrogen dioxide is not involved in this mechanism.