CO and NO: Pollutants or Miracle Molecules?
Carbon monoxide (CO) is a killer; everyone knows that. It is to blame for an estimated 3500 accidental deaths and suicides each year in the United States and is the number one cause of all deaths by poisoning. Nitric oxide (NO) is formed in combustion engines and reacts with oxygen to form nitrogen dioxide , the reddish-brown gas associated with urban smog. What most people do not know, however, is that our bodies cannot function without these molecules. A startling discovery made in 1992 showed that CO and NO are key chemical messengers in the body, used by cells to regulate critical metabolic processes. The toxicity of CO in moderate concentration is due to its ability to bind to hemoglobin molecules in the blood, thereby preventing the hemoglobin from carrying oxygen to tissues.
The high reactivity of NO leads to the formation of compounds that are toxic irritants. At the same time, though, low concentrations of CO and NO are produced in cells throughout the body. Both CO and NO are highly soluble in water and can diffuse from one cell to another, where they stimulate production of a substance called guanylyl cyclase. Guanylyl cyclase, in turn, controls the production of another substance called cyclic GMP, which regulates many cellular functions. Levels of CO production are particularly high in certain regions of the brain, including those associated with longterm memory. Evidence from experiments with rat brains suggests that a special kind of cell in the brains hippocampus is signaled by transfer of a molecular messenger from a neighboring cell. The receiving cell responds back to the signaling cell by releasing CO, which causes still more messenger molecules to be sent. After several rounds of this backand-forth communication, the receiving cell undergoes some sort of change that serves as a memory. When CO production is blocked, long-term memories are no longer stored, and those memories that previously existed are erased. When CO production is stimulated, however, memories are again laid down. NO controls a seemingly limitless range of functions in the body. The immune system uses NO to fight infections and tumors. It also is used to transmit messages between nerve cells and is associated with the processes involved in learning and memory, sleeping, and depression. Its most advertised role, however, is as a vasodilator, a substance that allows blood vessels to relax and dilate. This discovery led to (NO2)
the development of a new class of drugs that stimulate production of enzymes called nitric oxide synthases (NOS). These drugs can be used to treat conditions from erectile dysfunction (Viagra) to hypertension. Given the importance of NO in the fields of neuroscience, physiology, and immunology, it is not surprising that it was named Molecule of the Year in 1992.
AΝΑΔΗΜΟΣΙΕΥΣΗ ΑΠΟ ΤΟ ΒΙΒΛΊΟ "Fundamentals of General, Organic, and Biological Chemistry"
ΤΩΝ
John McMurry Cornell University
Mary Castellion Norwalk,Connecticut
David S. Ballantine Northern Illinois University
Carl A. Hoeger University of California,San Diego
Virginia E. Peterson University of Missouri,Columbia
3/3/2016
Carbon monoxide (CO) is a killer; everyone knows that. It is to blame for an estimated 3500 accidental deaths and suicides each year in the United States and is the number one cause of all deaths by poisoning. Nitric oxide (NO) is formed in combustion engines and reacts with oxygen to form nitrogen dioxide , the reddish-brown gas associated with urban smog. What most people do not know, however, is that our bodies cannot function without these molecules. A startling discovery made in 1992 showed that CO and NO are key chemical messengers in the body, used by cells to regulate critical metabolic processes. The toxicity of CO in moderate concentration is due to its ability to bind to hemoglobin molecules in the blood, thereby preventing the hemoglobin from carrying oxygen to tissues.
The high reactivity of NO leads to the formation of compounds that are toxic irritants. At the same time, though, low concentrations of CO and NO are produced in cells throughout the body. Both CO and NO are highly soluble in water and can diffuse from one cell to another, where they stimulate production of a substance called guanylyl cyclase. Guanylyl cyclase, in turn, controls the production of another substance called cyclic GMP, which regulates many cellular functions. Levels of CO production are particularly high in certain regions of the brain, including those associated with longterm memory. Evidence from experiments with rat brains suggests that a special kind of cell in the brains hippocampus is signaled by transfer of a molecular messenger from a neighboring cell. The receiving cell responds back to the signaling cell by releasing CO, which causes still more messenger molecules to be sent. After several rounds of this backand-forth communication, the receiving cell undergoes some sort of change that serves as a memory. When CO production is blocked, long-term memories are no longer stored, and those memories that previously existed are erased. When CO production is stimulated, however, memories are again laid down. NO controls a seemingly limitless range of functions in the body. The immune system uses NO to fight infections and tumors. It also is used to transmit messages between nerve cells and is associated with the processes involved in learning and memory, sleeping, and depression. Its most advertised role, however, is as a vasodilator, a substance that allows blood vessels to relax and dilate. This discovery led to (NO2)
the development of a new class of drugs that stimulate production of enzymes called nitric oxide synthases (NOS). These drugs can be used to treat conditions from erectile dysfunction (Viagra) to hypertension. Given the importance of NO in the fields of neuroscience, physiology, and immunology, it is not surprising that it was named Molecule of the Year in 1992.
AΝΑΔΗΜΟΣΙΕΥΣΗ ΑΠΟ ΤΟ ΒΙΒΛΊΟ "Fundamentals of General, Organic, and Biological Chemistry"
ΤΩΝ
John McMurry Cornell University
Mary Castellion Norwalk,Connecticut
David S. Ballantine Northern Illinois University
Carl A. Hoeger University of California,San Diego
Virginia E. Peterson University of Missouri,Columbia
3/3/2016
Δεν υπάρχουν σχόλια:
Δημοσίευση σχολίου