What Is Nitric Oxide?
Nitric oxide is a simple molecule consisting of one atom of nitrogen and one atom of oxygen. Little attention was given to this molecule until the 1970’s, when it was discovered that nitric oxide had blood vessel dilation properties.
All blood vessels are lined by endothelial cells. These cells act as selective filters that regulate the passage of gases, fluids and various molecules across their membranes. They are also instrumental in the production of the signalling molecule and free radical called nitric oxide. In the endothelial cells, a family of enzymes called nitric oxide synthase create nitric oxide from an amino acid called l-arginine, and oxygen. The mechanism behind this is for nitric oxide synthase to take a nitrogen atom from l-arginine, combine it with an atom of oxygen from molecular oxygen, and nitric oxide is created.
When nitric oxide is formed in the endothelium in blood vessels in the penis, it diffuses into the vascular smooth muscle cells of the penis where it binds to and activates an enzyme called guanylyl cyclase. This enzyme converts a molecule called guanosine triphosphate to another molecule called cyclic guanosine monophosphate (cGMP).
This serves as a messenger for many important cellular functions, including smooth muscle relaxation. When cGMP instructs the smooth muscles to relax, a surge of blood flow is allowed to freely pass into these smooth muscles, and the build-up of an erection starts. To learn more about the process behind penile erection on Truelibido, please go here.
This smooth muscle relaxation is paramount for a penile erection to take place, as the penis needs to be filled with blood in order for an erection to happen. No blood flow to the penis means no erection. The smooth muscles are ordinarily in a state of contraction, which means that they clench together and do not allow blood to flow to the penis, other than for regular maintenance purposes. On the other hand, when these smooth muscle relax, blood is allowed to flow into and engorge the penis.
The process is as follows: The nitrate is altered in the mouth and the digestive tract by bacteria that are normally present on the back of the tongue. These specialized bacteria use the nitrate to help them make energy in the form of adenosine triphosphate (ATP). In return, the bacteria utilize their own nitrate reducing enzyme called nitrate reductase to generate nitrite. Once in the stomach, gastric acids act on nitrites and convert them to nitrogen dioxide, dinitrogen trioxide and nitric oxide. The entire reduction process of nitrate into nitrite and then into nitric oxide occurs without the intervention of nitric oxide synthase.
In the late 1970s, researchers who were investigating the dilation mechanisms of the anti-angina drug nitroglycerine made a very interesting discovery. When nitroglycerine was administered to angina patients, it turned out to react with other chemicals in the body and subsequently convert into nitric oxide. And it was discovered that it was in fact this nitric oxide that produced the potent vasodilation effects of the blood vessels that benefited angina patients.
This finding initiated a whole new raft of research into nitric oxide. A rather profound breakthrough came in the late 1980s, when it was discovered that this nitric oxide acted as a neurotransmitter to erectile tissue. This lead to the development of the erectile dysfunction drug Viagra in 1989, although it was not approved for use to treat erectile dysfunction by the FDA in the U.S. until 1998. In 1998, three scientists received the Nobel Prize in Physiology for their discoveries of “nitric oxide as a signalling molecule in the cardiovascular system.” Nitric oxide was also named the molecule of the year in 1992.
Nitric oxide is what is called a free radical because it contains a single unpaired electron in its molecule. Hence it is very reactive, and has a half-life of only a few seconds. It is therefore not normally present in the body as nitric oxide, but reacts with other molecules to form more stable components such as nitrate. When nitric oxide is synthesized in the body, it has an almost immediate effect because of this very reactive property. At the same time, unless there is an adequate and persistent release of nitric oxide, the impact on blood vessels will wane quickly.
- It is a key signalling molecule throughout the body. Produced by the endothelial cells lining the arteries, it penetrates the underlying smooth muscles and acts as a potent vasodilator that relaxes the arteries. Therefore, nitric oxide plays a critical role in blood pressure and overall circulation, as well as in increasing nutrient and oxygen delivery to every system, organ, and tissue in the body.
- Nitric oxide acts as a neurotransmitter in the brain and is especially important in regards to learning and memory tasks that take place specifically in the hypothalamus. Nitric oxide is synthesized in the brain upon demand and can be used in cognitive tasks immediately after being formed.
- Nitric oxide improves brain functioning and reduces cognitive decline. This is because it enhances blood flow to the brain and also because it functions as a secondary neurotransmitter between nerve cells.
- Nitric oxide is important to the immune system as white blood cells use nitric oxide to fight off bacteria, parasites and viruses. Nitric oxide produced by white blood cells is toxic to these entities and therefore plays an important role in their destruction.
- Nitric oxide plays an important role in bone formation and remodeling of old and damaged bones, as nitric oxide is utilized by cells called osteoblasts which are responsible for the maintenance and growth of bones.
- During physical exercise, additional nitric oxide is produced by the endothelial cells in order to dilate the arteries. This enables blood flow to be increased and hence the muscles and other tissues can be supplied with adequate amounts of oxygen and nutrients.
- A wide range of cellular activity is regulated by nitric oxide including cell division, cell survival and cell movement.
- Nitric oxide facilitates sleep and particularly REM sleep, and it also improves sleep recovery. Sleep apnea syndrome is correlated with decreased levels of nitric oxide.
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