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Poison and Panacea
| Article
# : |
11870 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
1 / 1994 |
2,376 Words |
| Author
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Jerry Shine
Jerry Shine is a freelance writer based in Somerville,
Massachusetts. He expresses his sincere thanks to Martin Kaye,
manager of the Bay of Fundy Marine Resource Centre in
Cornwallis Park, Nova Scotia, for his expert review of the
manuscript. |
Ten years ago, the nitric oxide (NO) molecule was thought of as little more than a simple, potentially toxic substance found in cigarette smoke and automobile-exhaust fumes. You didn't want to breathe it. NO was associated with acid rain, ozone depletion, and possibly cancer. It was considered a villain among molecules, and if they had made a movie about it, Vincent Price would have been given the part.
That being said, imagine the shock waves that rumbled through medical circles when it was learned that NO is manufactured naturally throughout the body and plays a crucial role in regulating the function of virtually every organ. It operates in the heart, brain, liver, kidneys, pancreas, lungs, uterus, and eyes. It helps regulate blood pressure, digestion, and even penile erection. It may play a role in protecting the body against infection. On the negative side, it's been implicated as a cause of blocked arteries, congestive heart failure, and possibly AIDS-related dementia, Huntington's disease, Parkinson's, and Alzheimer's. It all depends on what substances it combines with in the body.
If you're starting to get the feeling that NO is just about everywhere, you're right. "It's really fascinating from an evolutionary standpoint that there are all of these genetically distinct enzymes throughout the body that use nitric oxide for such a diverse range of biological functions," says Dr. Thomas Michel of Brigham and Women's Hospital in Boston. "All of this came as quite a surprise."
The mystery unfolds
Hindsight being 20/20, NO's biological import probably shouldn't have come as a shock. Clues hinting at its significance began popping up 100 years ago, when nitroglycerin was first used to treat angina, a condition caused by the lack of sufficient oxygen to the heart. Although it wasn't known then, nitroglycerin can't become active in the body until it's been metabolized and broken down chemically into N0, which then relieves the painful chest symptoms angina causes.
NO's presence in the body remained unknown, however. When researchers found that people with infectious conditions excrete more nitrates than usual, the way opened to make this connection. When someone is sick, important fighters against the infection are macrophages, the scavengers of the immune system that engulf and devour invading organisms. Dr. Michael Marietta of the University of Michigan determined that macrophages produce nitrates when they are fighting infection.
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