cGMP mediated smooth muscle vasodilators

cGMP-mediated smooth muscle vasodilators, as their name implies, are medications that promote dilation of blood vessels by potentiating the effect of cyclic guanosine monophosphate, or cGMP for short. These medications are mainly used to treat hypertension, heart failure, and angina pectoris, which is a pain caused by reduced blood flow to the heart muscle. All right, first, let’s focus on the structure of blood vessels. Blood vessels have three layers, also called “tunics,” or coverings, that surround the vessel lumen, which is the hollow part of the vessel that contains the blood. The innermost tunic is the tunica intima, which includes the endothelial cells; the next one is the tunica media, or middle tunic, which is mostly made of smooth muscle cells and sheets of elastin protein; and finally, there’s the tunica externa, or outside tunic, which is made up of loosely woven fibers of collagen. Moreover, the tunica media can contract, causing vasoconstriction, where the lumen gets a lot smaller; or it can relax, or vasodilate, causing the lumen’s diameter to increase, allowing for more blood flow.

Now, within endothelial cells of the tunica intima, there’s an enzyme called nitric oxide synthase, which uses the amino acid L-arginine and molecular oxygen to synthesize nitric oxide or NO for short. Once synthesized, nitric oxide diffuses to adjacent smooth muscle cells in the tunica media, where it binds and activates an enzyme guanylyl cyclase. This enzyme converts guanosine triphosphate, GTP, into cyclic guanosine monophosphate, cGMP, which is a second messenger that induces relaxation of smooth muscle cells in vessel walls. All right, now moving on to pharmacology. cGMP-mediated smooth muscle vasodilators are subdivided into two main groups: antianginal medications, which are used to treat anginal pain, when oxygen delivery to the heart is inadequate for normal heart function; and antihypertensive medications, which are used to treat high blood pressure.