NITRIC OXIDE: Molecules of biological interest.

Is nitric oxide a hormone?

Nitric oxide (NO) is a simple ubiquitous signaling molecule and plays important roles in almost every biological system. Recent evidences suggest that NO may act as an endocrine molecule. The aim of this review is considering available literature on endocrine roles of NO and/or its metabolites, i.e., nitrite and nitrate. Existing data suggest the idea that NO is a hormone that after production in tissues, it is stabilized and transported as nitrite and/or S-nitroso thiols in the blood to target cells. Nitric oxide (NO), a highly reactive gas transmitter, is critical for a number of cellular processes and has multiple biological functions.

Nitric Oxide and Its Clinical Applications

Nitric oxide (NO) has long been known as endothelium-derived relaxing factor. It is a vasodilator, modulating vascular tone, blood pressure and hemodynamic, a role exploited by nitrate donor therapy for angina, heart failure, pulmonary hypertension and erectile dysfunction. In addition, its powerful antioxidant, anti-inflammatory and antithrombotic actions are antiatherogenic with ant atherothrombotic impact.

Nitric Oxide Functions

Nitric oxide is a compound in the body that causes blood vessels to widen and stimulates the release of certain hormones, such as insulin and human growth hormone.

NO is a potent signaling molecule, a key determinant of endothelial function, metabolic and vascular health, also affecting the nervous and immune systems. Protective effects occur at pico- to nanomole NO concentrations. At higher concentrations, NO and its derivatives become cytotoxic.

Nitric Oxide & Skeletal Muscle

NO signaling in skeletal muscle is implicated in the control of multiple functions, including

• muscle metabolism,

• excitation-contraction coupling and contractility,

• immune function,

• cell growth and

• neurotransmission.

Metabolically active skeletal muscle is the most abundant tissue, constituting approximately 40% of normal-weight body mass, rendering it a critical factor in total-body metabolism. Skeletal muscle NOS thus plays a pivotal role in total-body glucose and lipid homeostasis.

   What is the role of nitric oxide in the body?

Some of the known functions of nitric oxide are listed in the table below.

Cardiovascular system	Controls vascular tone. Relaxes vascular smooth muscles and reduces blood pressure. Dilates vessels and relieves the pain of angina. Inhibits the aggregation of platelets within the vessels and prevents thrombotic events.
Nervous system	Acts as a neurotransmitter, including in the autonomic nervous system. Increases cerebral blood flow and oxygenation to the brain. One of the important mediators in penile erection during sexual arousal.
Lungs	Dilates pulmonary vessels. Beneficial in Adult Respiratory Distress Syndrome, Pulmonary hypertension and Chronic Obstructive Airway Disease. Produced in abnormal amounts in inflammatory lung conditions. Concentration of NO in exhaled air is a marker of airway inflammation.
Gastrointestinal tract	Regulates the relaxation of smooth muscles. Control’s peristalsis and the function of sphincters.
Renal system	Due to its vasodilatory effect, increases blood flow to the kidney. Increases the glomerular filtration rate and the production of urine.
Immune system	Modulates T cell-mediated immune response.

 Nitric oxide production is essential for overall health because it allows blood, nutrients and oxygen to travel to every part of your body effectively and efficiently.

In fact, a limited capacity to produce nitric oxide is associated with heart disease, diabetes and erectile dysfunction.

Fortunately, there are many ways to maintain optimal levels of nitric oxide in your body.

Factors that reduce NO bioavailability

Increase Nitric Oxide Naturally

Nitric oxide is a molecule that’s produced naturally by our body, and it’s important for many aspects of your health.

Its most important function is vasodilation, meaning it relaxes the inner muscles of the blood vessels, causing them to widen and increase circulation.

Nitric oxide is a very simple but important molecule. It is not the same as nitrous oxide, or “laughing gas.” The nitric oxide story is no laughing matter; it will determine how long you live. And it's an integral part of sex and heart health.

Highlights

●Oxygen is a major determinant of the rates of nitric oxide synthesis and metabolism.

●Under biological conditions nitric oxide only reacts with metals and other free radicals.

●Oxygen determines the half-life, concentration, and diffusional distance of nitric oxide.

●Proteins respond to nitric oxide in a concentration and time-dependent manner.

●Oxygen and the redox environment will greatly influence signalling responses to nitric oxide.