Appearances can be deceiving! An age-old, tiny compound such as nitric oxide, which is easily lost among the myriad of other intricate neurotransmitters of its calibre, seems an unlikely candidate for induction into the Chemical Hall of Fame. However, since the discovery six years ago that it is a vital neurotransmitter, nitric oxide has proved its worth countless times through its applications in the area of medicine, Constantly discovering monumental new functions of nitric oxide, scientists can hardly believe the potential. "In my 25 years of research, I have never seen a molecule [nitric oxide] that so pervasively influences normal and abnormal body functions" (Talan 1993), said the director of neuroscience at Johns Hopkins Medical School, Dr. Solomon Snyder. This compound has turned the collective head of the science world such that it was nominated "Molecule of the Year" by Science magazine in 1992.
Discovered in 1772 by the renowned Joseph Priestley, who also discovered oxygen, nitric oxide is a clear, colouriess gas under normal atmospheric conditions with the chemical formula NO. It is formed of nitrogen which comprises eighty percent of our atmosphere, and oxygen which comprises the other twenty percent. A highly reactive compound, it only exists for six to ten seconds inside the body, then it is converted, by oxygen, into other compounds of nitrogen called nitrites. Uniquely, it is one of the few compounds with an odd number of electrons thereby making it a free-radical' prone to ionizations.
As one of the simplest compounds in nature, nitric oxide had been overlooked as an important factor to the body's chemistry. Due to recent exposure however, thousands of new studies are being conducted concerning its applications. For example, the role of nitric oxide in helping our immune system fight disease has been established. When our body notifies the immune system of an invader, our system uses other compounds to create nitric oxide. The nitric oxide in turn allows the macrophageS3 to devour such invaders as bacteria, fungi, and tumour cells.
Nitric oxide has also been identified as a "messenger molecule" (Bredt and Snyder, 1969). In 1987, scientists working independently of each other in California and in England first revealed nitric oxide as a neurotransmifter. They were trying to identify the compound that caused the layer of cells that line the heart and blood vessels to relax. Finding that when the neuro- chemical acetylcholine4 hit the surface of these cells it released nitric oxide, scientists observed the relaxation of the muscles adjacent to the layer of cells. This discovery led to new breakthroughs toward better treatments for angina, hypertension, and other serious heart problems. Nitric oxide, since it is now understood to be the principal regulator of blood pressure, is leading the old drug nitroglycerine in related breakthroughs.
Inside the brain, nitric oxide has always existed, but it has started to receive its rightful credit only recently. In nerve cells, the role that nitric oxide takes is "comparable in importance to its functions in macrophages and blood vessels, perhaps even more so" (Bredt and Snyder, 1974). It is unlike any known neurotransmitter; unstable and stored in the cytoplasm, it is likely produced on demand in the neuron. Its roles in the brain have been linked in the last six years to learning and memory, and to treatments for stroke and for Alzheimer's and Huntington's diseases.
As a testament to its astonishing purview, nitric oxide offers benefits not only to the treatment for chronic illness but in trauma treatment as well. Patients with respiratory distress treated with nitric oxide gas had an increased survival rate from 50% to 80%. The gas discourages blood flow from wet, unventilated areas of the lungs resulting in more effective respiration. Furthermore, by treating babies born with Down's syndrome with nitric oxide before and after the babies underwent reparative cardiac surgery, the results were more effective than simple oxygen in reducing pulmonary pressure and promoting the oxygenation of the blood.
Misunderstood, nitric oxide, the biological 'jack-of-all-trades', has been viewed by the public negatively. It is believed to be only a poisonous gas which is a cause of acid rain in polluted air. However, the governments of both Canada and the United States agreed in the late 1980s to "freeze emissions of nitrogen oxides" (Globe and Mail, 1988). With modern filter technology, this freeze has significantly cut harmful emissions.
This unique gas, which is integral to biological functions in humans, speaks volumes of its merits with every heartbeat of every person. It is undeniably an awe-inspiring feat of nature.
1. A free-radical is an atom or group of electrons having at least one unpaired electron.
2. Ionization is the addition or removal of one or more electrons to or from an electrically neutral atom or molecule to form ions.
3. A macrophage is a large cell which is dispatched by the immune system to eat any invaders such as bacteria, fungi and tumour cells.
4. Acetylcholine is a neurochemical which carries chemical signals between cells.
1. Bredt, David S. and Snyder, Solomon, H. "Biological Roles of Nitric Oxide", Scientific American, May 1992, pages 68-72.
2. Hixson, J.R. "Nitric o)dde-making a name for itself', The Medical Post, 15 March 1994, page 45.
3. Horgan, John "Neural Eavesdropping", Scientific American, May 1994, page 16.
4. Microsoft Bookshelf U.S.A., Microsoft, 1992.
5. "Nix on NOx.", Popular Science, July 1994, page 24.
6. Snyder, Solomon H., "Nitric Oxide: First in a New Class of Neurotransmitters?", Science, Volume 257, 24 July 1992, pages 494-96.
7. Talan, Jamie, "The healing powers of riitric oxide", Montreal Gazette, 26 September 1993, page C5.
8. "U.S. freeze approved on key air pollutant.", The Globe and Mail, 26 February 1988, page A4.
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